The single-pass optical parameter mid-infrared(MIR)ultra-short pulse generation scheme based on the all polarization-maintaining fiber is verified experimentally. Based on the all-fiber master-oscillator-power-amplifier(MOPA)structure, an adjustable repetition rate near-infrared pulse is achieved with average power of 2.4 W, pulse width of 48.85 ps, and center wavelength of 1029.75 nm. When the repetition rate of the system is set as 100 kHz, the peak power of the near-infrared pulse can reach 491 kW. When the average power of the incident pulse is 608.9 mW, a mid-infrared picosecond pulse with an average power of 66.13 mW and corresponding peak power of 13.5 kW is obtained by pumping the MgO-PPLN crystal using the near-infrared pulse. By adjusting the crystal reversal period and temperature, the tunable wavelength output of 3180-3976 nm can be achieved. The proposed scheme has the characteristics of simple structure and high stability.