Several pulse compressing techniques of 10 GHz gain switch semiconductor laser output pulses are stuided via methods of theoretical analysis, numerical simulation and experiment. A novel three stage compressing technique is proposed which includes 1) compensation by normal dispersion fiber, 2) compressing by normal dispersion fiber followed by anomalous dispersion fiber, 3) compressing by comb like dispersion profile fiber (CDPF). In this experiment, the compressed pulse width of 2.8 ps is obtained and the total compressing factor is 9. This technique is important for implementation of 80 Gb/s optical time domain multiplexing system.