Abstract: Using waterproof installation, a study was carried out to test the effects of P and irrigation during grainfilling stage on the photosynthetic rate, the parameters of chlorophyll fluorescence induction kinetics,the grain filling process and the yield of winter wheat in the fluvoaquic soil area where available P is deficient The results showed that under the condition of no irrigation during the whole life of winter wheat, the opening and closing of stoma were stressed because of waterdeficiency during the grainfilling stage,the photosynthetic rate of winter wheat declined, while water use efficiency rose. Irrigation improved the photosynthetic rate and the apparent photosynthesis quantum efficiency Under the same watersupply level, light response of photosynthesis and the apparent photosynthesis quantum efficiency grew with P increase Winter wheat being irrigated possessed higher values of PSII and Fv/Fm,and lower value of NPQ The rate of grain filling has a positive correlation with P and water The effect of irrigation on accelerating the grain filling increased with fertilizer P supply rising P also increased plant height, spikes number, spikes length and panicle number The effect of P on the yield of winter wheat is more remarkable than that of irrigation in this experiment Economic coefficient declined with the improvement of watersupply level and P rate This study suggests that to save water it is necessary to apply plenty of fertilizer P for winter wheat in fluvoaquic soil area 