Abstract: Many reports have dealt with the effects of phosphorus deficiency on photosynthesis,but few researches(focused) on the effects of P under normal and excessive condition on the crop photosynthesis and yield components.In order to clarify the possible mechanism of phosphorus nutrition on various aspects of photosynthetic metabolism and yield characters,and to provide the scientific support for phosphorus fertilization recommendation,a field experiment was conducted on the Teaching and Demonstration Farm of Agricultural University of Hebei during 19992001 with a winter wheat(Triticum aestivum L.) cultivar Henong 859 as the test crop.The three phosphorus fertilization levels selected were P2O5 75,225 and 375(kg/ha).The results showed that,within the scope of in vitro phosphorus fertilization(75375(kg/ha),) the Pn,Gs,Chl,Pro and ATPase activities were increased,the RSP and PAD were prolonged,but the intercellular CO2 concentration(Ci) changed irregularly with increasing of phosphorus application rates.Under high phosphorus level(375 kg/ha),Chlb content,Hill reaction and non-cycle photophosphorylation activities of flag leaves were retarded,and these parameters showed a similar regularity change indicating they were more sensitive to phosphorus than the other parameters determined.The Pn of flag leaves,however,was still quite high under the high phosphorus level(375 kg/ha),resulting in the highest yield components and grain yield.We concluded that in spite of the high response sensitivity of Chl b content,Hill reaction and non-cycle photophosphorylation activities to P,they slightly affected carbon assimilatory within the certain range and should not be considered as the major limiting factors of photosynthesis.