In this paper,the mechanism of overshoot effect in high power fiber laser is analyzed,and a suppression method of overshoot effect based on pump modulation is proposed.Based on the linear constant current closed-loop negative feedback technology,the pump modulation is realized to prevent the excessive accumulation of inversion particles in the fiber laser oscillator,and finally the overshoot effect of high-power fiber laser is suppressed.A 750 W fiber laser system is built,after the pump modulation,the overshoot of 1450 W laser is attenuated by -2.86 dB,and the slow rise time of the rated power is less than 1ms.