State television broadcast images of Jing Haipeng, Liu Wang and China’s first female astronaut, Liu Yang, smiling after completing the exercise.
The docking is seen as a key step in the building of a space station, which China hopes to finish by 2020.
A manual docking procedure would be used in the event of a failure with the automated system.
It is regarded as a difficult manoeuvre, bringing gently together two orbiting vessels travelling at thousands of miles an hour.
Liu Wang had been expected to take charge of the operation, while Liu Yang was to conduct aerospace experiments, according to Agence France-Presse news agency.
Manual docking was mastered by the USSR and US in the 1960s.
The Shenzhou-9 spacecraft was launched on 16 June.
It carried out a successful automatic docking when it reached the Tiangong-1 module on 18 June.
Every move of the mission has been watched with patriotic pride by China’s state media.
Even the astronauts’ first space meal – rice, pickled pork, barbecue sauce and tea – was reported, our correspondent says.
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