In order to realize the laser ranging of Chang′e-4 repeater satellite, the study of lunar laser ranging (LLR) is needed to be carried out for technical verification. Yunnan Observatories of Chinese Academy of Sciences develops a common optical path LLR system based on the 1.2 m telescope. After many technical difficulties are overcame, the echo signal from the Apollo 15 reflector on the lunar surface was successfully detected on January 22, 2018, and the LLR is realized. Repeated experimental results show that the LLR system has the ability to detect very weak laser signals, and the measurement accuracy of the system reaches meter level.