The output characteristics and their influence factors of a fiber laser with high repetition rate and narrow pulse width based on master-oscillator power amplifier (MOPA) architecture are experimentally investigated. Under the condition of high output power, the impacts of the stimulated Raman scattering (SRS) on the gain characteristics and laser spectrum characteristics are analyzed through experiments. It is pointed out that SRS effect is the main restriction of power increases of fiber laser. By increasing the effective mode-field area and shortening the length of fiber, stimulated Raman scattering is suppressed successfully. The average output power of 64 W is achieved at repetition rate of 50 kHz with a pulse width of 14 ns. Meanwhile, the impacts of the fiber bending diameter on the output characteristics of laser are also experimentally investigated. The results show that reducing the diameter of bending properly can improve beam quality of output laser in a certain extent.