at 8.5 hours by Ye Guangfu and Li Guangsu, I presume 8 hr 30 min. The world's longest spacewalk was 8 hr 56 min carried out by US astronauts in Mar, 2001. This could be the world's second longest spacewalk if it’s 8 hr 30 min, if not then third longest. Their task was to install space debris protection panels on the CSS.