The experimental study on an ultrashort laser amplifier using a domestic Yb3+-doped large-mode-area fiber as gain media was presented. The seed pulse has a width of 2.3 ps and repetition rate of 95 MHz, provided by an all-solid-state mode-locking laser designed by ourselves. The pump source is a 976 nm fiber-coupled laser diode (LD). The output pulse with the average power of 2.41 W from the 1.6 m gain fiber is achieved under the input pump power of 11.2 W, while the seed pulse average power is 100 mW. The amplified energy per pulse is up to 25 nJ. The width of the pulse is broadened from 2.3 ps to 3.0 ps, synchronously.