Abstract: In view of the fact that the previous structural plane classification methods are mostly macro-qualitative analysis， which is not conducive to guiding actual engineering design and construction. A quantitative structural plane classification method based on the improved ideal point model was proposed. Firstly， considering various factors of structural plane classification， seven indicators were used for quantitative characterization， and a multi-index structural plane quantitative classification system was established. Then， based on the principle of minimum entropy， the weights obtained by analytic hierarchy process and entropy weight method were optimized， and the ideal point model was improved to obtain the optimal combination weight. Finally， the improved model was applied to the structural plane classification of Xinglong tunnel in Chongqing and compared with the actual engineering. The results show that the classification results obtained by improved ideal point model are consistent with the actual project， with an accuracy of 93.3%， which has strong reliability and engineering practicability. It can provide a new idea and method for rock mass structural plane classification.

Key words: structural plane classification; ideal point model; analytic hierarchy process(AHP); entropy weight method; combination weight