The master oscillator power amplifier (MOPA) based on end pumped slab gain medium is one way to develope high average power laser diode pumped laser (DPL), attracts widespread attention in recent years. By using theoretical analysis and numerical simulation, the design models of slab gain module are established, and then the small-signal gain coefficient, the output characteristics, the temperature and the thermal stress of the slab gain module are obtained. The size of module is 50 cm(length)×30 cm(width)×20 cm(height). The static wavefront distortion is 0.22 μm (excluding tilt). The uniformity of fluorescence distribution is achieved by 94%. The average output power is achieved by 1086.3 W at duty cycle of 60%, and the slope efficiency is 41.7%.