Clause selection is the core part of Automated Theorem Prover （ATP）， the ability and efficiency of ATP can be improved by optimizing the clause selection method. At present， although the traditional one-by-one filtering method based on attribute priority can realize clause selection， it is difficult to evaluate clause comprehensively and lacks flexibility. Therefore， a dynamic clause selection method based on AHP_TOPSIS was proposed. In the method， the weight of each attribute of the clause was calculated by Analytic Hierarchy Process （AHP）， and then the clauses were evaluated and ranked by combining the weight results with Technique for Order Preference by Similarity to an Ideal Solution （TOPSIS）， thereby providing a basis for clause selection. In the AHP， considering the dynamic change of clause attributes， the methods of stage awareness and smooth transition were introduced. This enables the judgment matrix to be adjusted dynamically according to the derivation process， thus extending the AHP to the dynamic AHP. Meanwhile， according to the above clause selection method， the corresponding algorithm was implemented and applied to the first-order logic theorem prover CSE （Contradiction Separation Extension） to form a new prover CSE_AT. This prover was used to test the first-order logic problems in the TPTP （Thousands of Problems for Theorem Provers） problem bank from 2021 to 2024. Experimental results show that CSE_AT proves 22 more theorems than CSE， and most of the theorems proved by CSE_AT have Rating value in the range of ［0.6，0.9］. It can be seen that the AHP_TOPSIS-based dynamic clause selection method can optimize the deductive paths， so as to improve the proof ability of the prover.