Aiming at the uncertain and complicated problem of evaluation and calculation of the strength of transmission tower material, a method of rough fuzzy sets has been proposed in this paper for the precise calculation of actual strength of the transmission tower material. Firstly, this method use rough sets theory to reduce index set, then by adopting the combination of subjective weight and objective weight method to determine evaluation index weights, and according to the established evaluation level set, the actual strength of tower material is evaluated and calculated by the method of fuzzy mathematics. Example analysis results show the correctness and feasibility of the calculation method, it can solve the typical and uncertain problem of the factor validity which is not clear in the evolution process of tower material intensity, and it can provide important scientific for transmission line structure safety assessment.