A master oscillator power amplifier (MOPA) structure based on Nd∶YAG microchip and Nd∶YVO4 slab is reported. The master oscillator is a passive Q-switched Nd∶YAG/Cr4+∶YAG microchip laser, and the seed laser with pulse energy of 82 mJ and pulse width of 1ns is obtained when the repetition frequency is 1 kHz. In the amplifier, an output pulse energy of 2.3 mJ with peak powers reaching 2 MW and pulse width of 1ns is obtained while the oscillator provides the amplifier with a 82 mJ input. Meanwhile, the M2 factor of beam quality is measured to be 2.48 at x direction and 1.24 at y direction. This laser systerm is compact and air-cooled, the fluctuation of output energy is below 4% when the temperature ranges from 15 ℃ to 32 ℃.