A indirect heating carbonization method is used to carbonize the wood chip from trimmed branches, and some technological parameters that influence the carbonization are studied. The parameters are main air inlet, carbonization temperature and carbonization time. The aim of the experiment is to optimize the technological parameters of the carbonization in order to provide technical support to the improvement of the ecological environment and the recycling of the waste in agricultural production. The results show that carbonization yield rate, carbon rate and the charcoals performance are maintained at a high level when the carbonization temperature is controlled at about 500℃, the carbonized time is set at about 12 h, the main air inlet is set at 5 000 mm2,and the chimney height is 2 m.