Abstract: In order to accurately assess the stability of the tunnel surrounding rock and solve the problems of ambiguity and randomness in the research process and the incompatibility of evaluation indicators, reduce the error caused by the single subjective and objective weighting method, and introduce the cloud model into the In the extension theory, the extension theory can be used to realize the conversion of contradictory problems to compatible problems, and the cloud model has the advantage of dealing with the double uncertainty of things. Combined with the ideal point combination weighting method, the stability evaluation of the tunnel surrounding rock is studied. Through literature survey and data statistics, select 6 representative indexes to form the tunnel surrounding rock evaluation index system, use the ideal point method to give the evaluation index combination weight, and construct an extension cloud model to comprehensively evaluate the tunnel surrounding rock stability. By applying this method to engineering examples and comparing with other methods, the results show that the method of tunnel surrounding rock stability evaluation based on the ideal point-extension cloud model can reduce the uncertainty in the evaluation process and overcome the single weighting method. The shortcomings have good applicability and can be applied to actual projects.