Pulsed laser with 100 MHz repetition rate and 1 ns pulse width is obtained by intensity modulating a continous wave (CW) single frequency fiber laser with 70 kHz line width. The spectrum line width of the modulated pulsed laser is less than 0.8 GHz. A combined amplification setup with a fiber amplifier and two solid-state amplifiers is used to achieve power amplification of the pulsed laser. The output average powers are 13 W and 32.9 W after first and second solid-state laser amplifier, respectively. The small signal of the modulated pulsed laser is firstly amplified up to 2 W by a fiber pre-amplifier. The pre-amplified laser transmits the two solid-state main amplifiers for further power amplification. The combined amplification setup effectively weakens the stimulated scattering and amplified spontaneous emission (ASE) in the fiber amplifier. After amplification, the output laser preserves line width of 0.8 GHz with pulse width of 1 ns and repetition rate of 100 MHz. Such a laser output with single frequency, narrow pulse width and high repletion rate is required in many special applications.