State TV showed Liu Boming, Tang Hongbo and Earth rolling past them from the airlock. Commander Nie Haisheng was the third member of the crew. He remained inside.
According to the Chinese space agency, Liu and Tang spent almost seven hours outside of the station.
The three-month trip will take them to China's third orbital station. It is part of an ambitious space program that also landed a robotic rover on Mars in May. The mission coincides with the 100th anniversary celebrations of the Communist Party.
The station's first module Tianhe (or Heavenly Harmony) was launched on April 29. The automated spacecraft was then launched with fuel and food. Liu, Nie, and Tang arrived aboard a Shenzhou capsule on June 17.
Liu secured his feet to a platform attached to the remote-controlled arm. This held Liu in place as he used an electric drill to install equipment.
China's space agency has plans to launch 11 rockets by the end of next years to add two modules to its 70-ton station.
Liu is a veteran from the 2008 Shenzhou 7 mission, when Zhai Zhigang took China's first spacewalk. Nie is currently on his third space flight, while Liu is his first. All three are military pilots.