Lidar technology based on high-energy narrow linewidth pulse lasers is widely used in the field of atmospheric remote sensing. An in-band core pumping pulsed fiber laser based on MOPA is introduced in this paper. The laser adopts a split design，in which the seed module can output laser pulses with a pulse energy of 1.8 μJ，and switch the center wavelength between 1 572.018 nm and 1 572.480 nm at a repetition rate of 1~100 Hz. Within the temperature range of 10~40 ℃，the center wavelength drift of the seed module output is not more than 0.58 pm，and the output pulse width is adjustable between 200~400 ns. The amplification module amplifies the output pulses of the seed module by using in-band pump. By suppressing the stimulated Brillouin scattering effect of the main amplification stage，high-energy outputs of 76.49 μJ at a pulse width of 200 ns and 135.7 μJ at a pulse width of 400 ns are achieved，with near diffraction limit spot and excellent spectral signal-to-noise ratio. The laser can be used as a source for differential absorption lidar and has practical significance in the field of remote sensing measurement of CO₂ gas concentration.