Blasting into space aboard a Long March 2FT1 rocket, the 8.5-ton module which will lay the groundwork for a future space station is to stay in orbit for two years.
China plans to launch an unmanned Shenzhou 8 spacecraft to practise docking manoeuvres within the next few weeks.
Two more missions, at least one of them manned, will meet up with the Tiangong-1 next year with astronauts staying for up to one month.
Two other experimental modules are to be launched for additional tests before the actual station is launched in three sections between 2020 and 2022.
Weighing about 60 tons when completed, the Chinese station will be considerably smaller than the 16-nation International Space Station, which is expected to continue operating through to 2028.
The space station is the most ambitious project in China's exploration of space, which also calls for landing on the moon, possibly with astronauts, and underscores the country's ambitions to become a major space power.
Both President Hu Jintao and Premier Wen Jiabao were at the launch.
China launched its first manned flight in 2003, joining Russia and the USA as the only countries to launch humans into orbit.