In order to investigate the effects of winter irrigation and irrigation during the key growing stage on crop growth and forage yield of siberian wildrye grass (Elymus sibiricus L.), field experiments were conducted in Bashang Plateau in the farming-pastoral ecotone of North China during 2005.10-2007.10. Rainfall, soil water content, plant height, leaf area index (LAI), biomass and forage yield were measured in field plots under no irrigation (CK), winter irrigation (W1), irrigation during key growing stage (W2), and the combination of W1 and W2 (W3). The results showed that forage yield was dominated by the first cutting due to the poor regrowing ability. The single irrigation during the key growing stage significantly improved the plant height, LAI and biomass of the first harvest. Forage yield of the first cutting under W2 was above 4500 kg/hm2, which was increased by 104% and 391%, respectively, in two years compared with CK. The grass under W1 turned green earlier in the following spring, and the forage yield of the first cutting was increased by 53% and 87%, respectively. There was no significant difference between forage yields under W3 and W2. Therefore, single irrigation during the key growing stage is recommendable for siberian wildrye grass in this region. In addition, the biomass and LAI increased with plant height linearly, which provides evidence for simulating the biomass and LAI of siberian wildrye grass.