A quasi continuous wave Nd∶YAG planar waveguide laser amplifier with a wavelength of 1319 nm is reported. The seed source is an oscillator based on a side-pumped rod Nd:YAG laser model, and the gain medium of the amplifier is a planar waveguide Nd∶YAG. The size of the YAG planar waveguide is 0.6 mm×10 mm×60 mm, the central area 0.1 mm×10 mm×50 mm is the doped region, and the surrounding area is undoped YAG. The pump source of the amplifier is a diode laser array, which is coupled from the rear end into the planar waveguide gain medium. The seed laser is coupled into the gain medium via the end facet, and a single-pass amplification is introduced. In order to achieve the good heat dissipation, two micro channel heat sinks are welded onto the Nd∶YAG planar waveguide. The end facets are coated high transmission at 1319, 1064 and 808 nm. When the driving current of the diode laser arrays is 110 A and the pulse repetition rate is 200 Hz, the output of 36 mJ 1319 nm laser is obtained, and the optical to optical efficiency is 8.3%.