A laser amplifier of LD pumping Nd: glass with a high beam quality and stability, which amplifies nanosecond laser pulse, has been developed in this paper. Under 1Hz repetition frequency, when the flat top pulse of 3 ns width and 1 nJ energy is injected as the seed pulse, the average output energy of the laser amplifier is 115.3 mJ with a net gain of 109, the energy dispersion degree of the outputting laser is no more than 2%; the modulation degree near field is less than 1.23:1.
