Experimental study on all-fiber high power pulse fiber laser based on 1064 nm gain-switched laser diode is reported.The method of tri-stage cascade amplification is employed in the experimental.The first stage amplification is single-mode ytterbium-doped fiber,and gain medium of the second and third stage amplification is double-cladding fiber.Average power of 25.3W is obtained under a maximum 45.2 W pump power,and the optical-optical efficiency is 55.9%.The pulse width is 223 ps with center wavelength of 1064 nm.No nonlinear effect is observed by spectrometer,and the SNR is beyond 30 dB.A higher power laser output can be realized as the pump power is further enhanced.