Abstract: The paper studied the effects of irrigation and PP333 on the seed yield and yield components in Jiuquan of Gansu province. The results indicated that there were optimal seed yield, fertile tillers/m2 and spikelets/fertille tiller for western wheatgrass, when at five times of irrigation, in turn green period, jointing period, earing period, filled period and flowering period, respectively, in the season of growth. The irrigation have been cautious not to bring on lodging. Jointing stage irrigation was in favor of fertile tiller and seed number, fertile tillers/m2 and seed number, the most productive factors in all the yield components, were significantly correlative with the yield; Sprinkling with oneoff 0.3 kg/hm2 PP333 of 0.022 5% in green period, which were remarkable effects on increasing the fertile tillers/m2,spikelets/fertille tiller, florets/spikelets tiller, seed/spikelets tiller and the seed yield; Irrigation with PP333 improved effectively seed/spikelets tiller and the seed yield. The effects of sprinkling with PP333 were better than irrigation with PP333.