Abstract: With the development of mining technology and the application of advanced mining equipment， most underground mines in China have gradually switched to trackless mining systems ， but rail mining systems have not been completely abolished， thus forming a trackless and rail combined mining system in some mining areas. In order to evaluate the synergistic effect of the composite mining process system composed of trackless and rail combined mining， based on the theory of coupling synergy degree evaluation and the coupling synergy degree measurement model， the trackless and rail combined mining area of Yunnan Tin Industry Co.， Ltd. was used as the project cases. Then， a coupling synergy evaluation system of mining technology system was constructed to carry out research on the evaluation of coupling synergy degree.The results showed that the benefit value T of the trackless and rail combined mining technology system of the Yunnan Tin Company was 0.65， the coupling degree C was 0.80， the coupling synergy degree D was 0.72， and the synergistic level of the system was "synergy". According to the evaluation results， the suggestions and measures for the optimization of the trackless and rail combined mining technology of the Yunnan Tin Company were proposed. The evaluation model and method provided a new idea for the evaluation of the synergy degree of other mining technology.

Key words: underground mine, trackless and rail combined mining, synergistic effect, coupling synergy degree, mining technology optimization