Since the coupling of environment corrosion and wind-induced vibration, the fatigue properties of structural members have degenerated during the service period, and the reliability of transmission tower-line system has also decreased gradually. However, both accuracy and efficiency can’t all be considered at the same time, whether the traditional quadratic response surface method with cross terms or not. In order to overcome this problem, an adaptive response surface method and an S-N curve model of Q345 equal angles are used to research the reliability of transmission tower-line system in this paper. At first, a criterion for judging the existence of cross terms is derived mathematically in the present work. Combing this criterion with quadratic polynomial of all possible terms via an indicative function, an adaptive response surface, which is more rational than traditional response surface, is proposed. And then, according to the fatigue test results of Q345 equal angles, a corrosion fatigue t-P-S-N surface expression is presented. Meanwhile, combing this t-P-S-N surface model with probability theory, a random t-P-S-N surface model of Q345 equal angles is also obtained. At last, the corrosion fatigue reliability of transmission tower-line system is studied based on the proposed t-P-S-N model and adaptive response surface. It is can be found from the results that: ①The criterion is accurate and effective. ② The proposed response surface is fair accuracy and high efficiency for reliability analysis.③The random S-N curve model of Q345 equal angles is simple and easy in structural reliability analysis.