At present,the codes of transmission towers are almost based on the construction of building codes,and the design objects are mostly aimed at the load-effect ratio not greater than 3.However,the living load effect of the transmission towers is higher than that of the existing codes,and the reliability of the components is reduced.In order to calibrate the reliability level of transmission towers,regarding the load-effect ratio as a random variable based on the point estimation method is firsly attempted,the weighted average reliability index of tower structure is obtained based on the distribution of load effect ratio as input.Firstly,the samples of wind load-effect ratio of tower structural members are obtained through a large number of structural analyses,and the distribution fitting is exploited to fit the distribution of load effect ratio.Secondly,applying the point estimation method,the abscissas of the fitted load-effect ratio distribution are selected,the reliability index of these points is calculated,and then the average reliability index according to the weight of each corresponding point.At last,the average reliability index under different wind speed and different structure importance coefficients is calculated.