With the increase of different types of space borne detectors and data capacity， as well as the expansion of the exploration field， requirements in the deep space exploration of ground communication rate and communication distance are also increasing. Compared with radio communication， space laser communication has several advantages， such as high data rate， narrow laser beam， higher security， terminal light-weight， and low power-consumption. Thus， it has great potential in deep space communication. However， space laser communication faces great challenges in the case of long distances. Generally， long-distance， high-sensitivity communication is performed by increasing the peak power of the transmit laser in the aircraft terminal， which increases the receiving area of the ground optical system， thereby improving the receiving sensitivity of the detector. By analyzing the number of photons reaching the surface of the detector， the PPM modulation system and superconducting nanowire single photon detector （SNSPD） is found to be significantly better for deep space laser communication. More specifically， the bit error rate （BER） of the system is derived from the detection probability and false probability of SNSPD. A receiving telescope array with an effective aperture of 10 m is composed of several telescopes through the combination of ‘or’ and ‘and’ signals. Subsequently， the BER of several different cascading modes is analyzed， and the results reveal that the BER with sixteen 2.5 m-aperture telescopes is relatively better than 10^-7 under strong background conditions， a communication distance of 2.67 AU， and a communication rate of 1 Mb/s.