Effects of phosphorus activator（PA） on amount of Olsen-P and corn yield in black soil were studied in order to conduct fertilizing rationally.The results showed that PA could slow the trend of decreasing of Olsen-P in black soil and enhance corn yield.H₂（450 kg/hm²） was the best PA which enhanced corn yield 9.32% more than CK.Following was citrate（15 kg/hm²） and HA（150 kg/hm²）,which enhanced corn yield 5.99% and 4.99% more than CK,separately.PA could enhance corn yield mainly through increasing 1000-seed weight and grain number per spike.Correlated analysis showed that correlation between corn yield and amount of Olsen-P at heading stage was best.It should be cautious to fertilize phosphates at heading stage.