1 hour 20 minutes. According to Baidu map, the distance from Daxing Airport to Renmin University is 59.5 kilometers, and it takes 1 hour for 20 minutes to take public transportation. This can be achieved:

1. Go 40 meters first, arrive at Daxing Airport, and take Daxing Airport Line. Arrive at Caoqiao after 2 stops.

2. Secondly, walk 10 meter to Caoqiao, take subway 19 line, go through 7 stops, reach Peony Garden, and walk 120 meter to Peony Garden.

3. Finally, take the outer ring of subway 10 line, after four stops, arrive at Huang Zhuang, Haidian, and walk 8 10 meters to China Renmin University.