Taking Nd:YAG planar waveguide as gain medium of a laser amplifier, we study the factors affecting optical-optical efficiency of laser with wavelength of 1064 nm during amplification. A free operational Nd∶YAG rod oscillator with wavelength of 1064 nm is used as seed source, and a diode laser array with wavelength of 808 nm is used as the pump source. The pulse width of pump beam is equal to that of seed, and the output of pump beam and seed is synchronous. The size of the Nd∶YAG planar waveguide is 60 mm×10 mm×1 mm, and the core thickness is 100 μm. The effects of seed energy, pump energy, and pump direction on the laser amplification efficiency are studied. The results show that when the input seed energy is 10 mJ, the quasi-continued laser with maximum energy of 713 mJ is obtained at the pulse repetition frequency of 100 Hz, the pump pulse energy is 1478 mJ, and the corresponding optical-optical efficiency is 47.6%.