Liu Yang, 33, an air force pilot, will join two male colleagues on board the Shenzhou 9 spacecraft, state-run news agency Xinhua says.
The spacecraft will dock with the Tiangong 1 space station module, as China bids to establish a permanent space base in orbit.
Liu will work on the mission with astronauts Jing Haipeng and Liu Wang.
"From day one I have been told I am no different from the male astronauts," Ms Liu was quoted by state broadcaster CCTV as saying before her assignment was announced.
"I believe in persevering. If you persevere, success lies ahead of you," she said.
Xinhua, which describes her as a veteran pilot who enlisted in the People's Liberation Army in 1997, said she was recruited to be an astronaut in May 2010.
The Shenzhou 9 mission, China's fourth manned space flight and its first since 2008, is expected to blast-off at 18:37 local time (10:37 GMT) from the Jiuquan launch centre in China's north-west Gansu province.
The astronauts aboard the Shenzhou 9 spacecraft will dock with the Tiangong 1 - an experimental module currently orbiting Earth - and carry out scientific experiments on board.
Last year, China completed a complicated space docking manoeuvre when an unmanned craft docked with the Tiangong 1, or Heavenly Body, by remote control.
This is China's first manned space docking mission, Xinhua says.