The invention discloses a transmission tower material actual strength calculation method with a practical result. Reduction is performed on a transmission tower strength influence factor set by use of a rough set theory; useful data is mined from a mass of historical data by use of a data mining method so as to construct a learning set; and constant iterative learning is performed by use of a gradient descent method according to the learning set so as to determine a factor set weight, and an acquired weight is evaluated comprehensively so as to calculate the degradation rate of the tower material actual strength. Through adoption of the method, typical uncertainty and nonlinear problems with obscure validity affecting the tower material strength factors in an evolutionary process can be solved. The method can provide an important scientific criterion for structure safety evaluation of the transmission tower.