Based on the stream flow at the debouchure of the Shulehe River from 1954-2010, and water supply, forest land, grassland area, crop type and its planting area at the irrigation district from 2000-2010, the impact of runoff change at the Shulehe River Oasis has been studied using system dynamics model under the background of climate change. The results showed that runoff change had significant effects on the oasis. If the runoff maintains the same growth trend in the future, the oasis area, agricultural output and ecological benefits would increase at different degrees; if the runoff decreases, the oasis area, agricultural output and ecological benefits would decrease accordingly. To be specific, if the runoff decreases by 5%, 10% and 15% in 2020, the oasis area and agricultural output would decrease by 4.5%, 8.9% and 13.4%. Therefore, putting water-saving project into practice positively and improving the utilization of canal system could tackle the adverse effect of runoff reduction in the future. Particularly, in a case of the runoff unchanged, if we spread conventional water-saving, forest land and grassland area would both increase by more than 16%, and if we spread efficient water-saving, the forest land area and grassland area would increase by 54.7%. If we improve the utilization of canal system to 0.70, the forest land and grassland area would both increase by more than 5% with a total output increasing by 5.4%, and if we improve the utilization of canal system to 0.75, the forest land and grassland area would both increase by more than 12% with a total output increasing by 12.2%.