The research of the distributed side-pump double-cladding pulse fiber amplifier is reported.A distributed sidepump,dual-stage all-fiber double-cladding pulse fiber amplifier is designed and developed with the home-made side-pump fiber couplers.The results of a high power,high repeat frequency all-fiber pulse fiber amplifier with a wavelength 1064nm,average output power 2.12W,pulse duration 20ns and a repeat frequency 50kHz is obtained.The max coupling efficiency and the minimal solation degree of the side-pump fiber coupler were 69% and 17dB respectively.The damage to the pump laser diodes of the backward high power pulse was avioded with the coupling method.Improving the coupling effeciency of the side-pump fiber coupler,the output power can be increased linearly.