Output laser beam of high power quantum well diode laser is linearly polarized, and Gran-Tayor prism can distinguish two laser beams in vertical polarizing direction by its characteristic of birefringence. If the input beams are in the opposite direction of the Gran-Tayor prism, they will be coupled into one beam. The experiment takes two 600 W diode laser stacks with 808 nm centre wavelength. The polarizing direction of one beam is changed by a 1/2 wave plate, the other is unchanged, and they are polarization coupled by the Gran-Tylor prism. The laser beam propagates through fast-axis or slow-axis collimating lens, focusing lens (f=100 mm) and slow-axis spherical aberration correcting lens. When the working current is 130 A, the electro optic efficiency is about 43%. Measured with the UFF100 laser beam diagnostics meter, the focal spot is rectangular, the area is 0.547 mm×5.0 mm, the fast-axis beam parameter product is 26.1 mm·mrad, and the highest output power is 1 kW. The laser system works stably.