Aiming at the low receiving power of space laser communication, a real-time space laser Pulse Position Modulation (PPM) communication system with high receiver sensitivity is designed and implemented in this paper and the transmission rate of this system is 800 Mslot/s. The experimental results show that, after using Erbium Doped Fiber Amplifier (EDFA) and optical filter, under the condition of -58.3 dBm optical input, the Bit Error Rate (BER) of the system before error code correction is 1.4E-4 and the system has ultra-high receiver sensitivity.