As the Sun becomes an expanding red giant and threatens to engulf the Earth in 100 years, the United Nations, now renamed as the United Earth Government (UEG), decides to proceed with the Moving Mountain Project, the pilot program to build thousands of gigantic ion engines that can propel the Earth out of the Solar System towards another habitable star system. In doing so, the UEG shuts down and bans the Digital Life Project (DLP), a radical group who believe humanity’s future is in digital immortality by developing mind uploading technologies, despite skepticism and increasingly violent protests from the public.
The first phase of the Moving Mountain Project is to build and test an ion engine on the Moon. However, a series of terrorist attacks by well-armed DLP supporters on the UEG facilities in 2044 resulted in a hacked drone attack on the space elevator in Libreville, Gabon, as well as a coordinated hacking of the elevator vehicles by highly trained infiltrators, with the aim of destroying the Ark Space Station supplying the lunar operation. Although UEG trainee astronaut Liu Peiqiang and his fellow trainees manage to defeat the hijackers on their vehicles, both the space elevator and Ark Space station are critically damaged and crash down to Earth.
To restore public faith in the Moving Mountain Project, Liu Peiqiang and other UEG engineers are sent to the moon to work on finishing construction of three lunar engines, which are prototypes to demonstrate the function before installing the first engines on Earth. Along with this, computer engineer Tu Hengyu, who had previously worked on the Digital Life Project before it was banned, works on incorporating the new 550 Series quantum computer,which was the original edition of 550C, will both control the highly efficient automated construction of the engines, and also control the operation once the engines are to be tested. Tu, in his spare time, views a simulation of his daughter, who had died in a car crash; but due to the limitations of the computer 550A, her digital consciousness can only live for two minutes before restarting. However, the computer of 550C was damaged and he needed to use 550A for the testing. Tu had to accept it, but asked Ma Zhao to invent future versions of the 550 series.
In the next 14 years, the UEG quells the DLP supporters, gathers resources and builds over 7000 engines that stop the Earth’s rotation. The Moving Mountain Project is officially renamed as the Wandering Earth Project, and the three completed lunar engines start to propel the Moon away from Earth. In 2058, Tu Hengyu decides to upload the recorded consciousness of his deceased daughter into the latest 550W supercomputer. Immediately after doing this upload, the lunar engines fire and then explode, sending the Moon on a collision course towards Earth.
To deal with the Moon crisis, the UEG initiates a backup plan that involves detonating all of the Earth’s nuclear weapons on the lunar surface and triggering its implosion. The mission faces numerous setbacks due to the difficulties in nuclear code decryption, the flooding of Internet root server data centers that allow coordinated detonation control, and the short time window before the moon reaches the Roche limit and fragments into pieces which will destroy the Earth. As lunar debris started falling to the Earth and hitting different cities, such as Beijing, Earth’s population grew increasingly restless and was on the verge of losing all hope. After the code deciphering hits a deadlock, hundreds of astronauts over the age of 50 voluntarily sacrifice themselves in order to manually detonate the nukes. Liu narrowly survives the nuclear detonation, managing to pilot a capsule back to the Navigation Space Station. Meanwhile on Earth, Tu, who is sent to help reboot the flooded Beijing server, uploads a copy of his own recorded consciousness into the network before drowning. His digital self manages to reboot the last Internet server in time, activating the Earth engines en masse and moving the Earth away from the course of the lunar debris. The Wandering Earth Project then officially begins with the Earth’s course towards Jupiter.
In a mid-credits scene, Tu’s digital self is addressed by the 550W artificial intelligence, who now goes by the personified name “MOSS” (“550W” upside down). The now-sentient supercomputer reveals that it has been behind every crisis that has ever harmed humanity’s efforts to save themselves, adding that it will also trigger many more in the future.