Abstract: Pot experiments were conducted using Yoshida culture solution with two rice varieties(Wuyujing-3 and Yangdao-6) to study the effects of glutamine synthetase inhibitor methionine sulfoximine(MSO) and photorespiration inhibitor isonicotinyl hydrazine(INH) on the ammonia volatilization rate(AVR),photorespiration rate(Pr) and glutamine synthetase(GS) activity in rice.The results showed that:(1)MSO decreased the Pn,but increased the Pr in the flag leaf;INH decreased the Pr significantly and Pn slightly.(2)MSO decreased GS activity,which promoted an increase in AVR in rice canopy.INH showed a slightly positive effect on the decrease in AVR.(3)Based on the comparison between the two tested varieties,the higher AVR variety(Yangdao-6) showed greater GS activity and lower Pr than those of the lower AVR variety(Wuyujing-3).