The safety issues related to explosion venting of hydrogen-air mixtures are significant and deserve more detailed investigation. Vented hydrogen-air explosion has been studied extensively in vessels with a single vent. However little attention has been paid to the cases with more than one vent. In this paper, experiments about explosion venting of rich hydrogen-air mixtures were conducted in a cylindrical vessel with two symmetrical vents to investigate the effect of vent area and distribution on pressure buildup and flame behaviors. Venting accelerates the flame front towards the vent but has nearly no effect on the opposite side. The maximum internal overpressure decreases and the maximum external flame length increases with the increase of vent area. Two pressure peaks can be identified outside of vessel, which correspond to the external explosion and the burnt gas jet respectively. Compared with single vent, two vents with same total vent area leads to nearly unchanged maximum internal and external overpressure but much smaller external flame length.