20MnTiB steel is the most widely used high-strength bolt material for steel structure bridges in China and its performance is of great significance to the safe operation of bridges. High-strength bolts used in steel bridge usually serviced in humid atmosphere for a long time. Factors as high humidity, high temperature and the settlement and absorption of harmful substances in the environment are very easy to cause corrosion of the steel structure. Corrosion will lead to section loss of high-strength bolts, produce lots of defects and cracks. And these defects and cracks will continue to expand, so as to reduce the life of high-strength bolts and even led to its fracture.Based on the investigation of the atmospheric environment in Chongqing in recent years, the corrosion solution to simulate the humid climate of Chongqing was designed in this study, and the stress corrosion experiment of high-strength bolts in the simulated humid climate of Chongqing was carried out. The effects of temperature, pH and concentration of simulated corrosion solution on the stress corrosion behavior of 20MnTiB high-strength bolts were studied.Chinese researchers tested the properties of 20MnTiB steel commonly used for grade 10.9 high-strength bolts at high temperature in the range of 20–700 degree Celsius and obtained the stress–strain curve, yield strength, tensile strength, Young’s modulus, elongation and expansion coefficient. They analyzed the fracture of 20MnTiB high-strength bolts used in steel bridge through chemical compositions examination, mechanical properties test, microstructure examination, the macro and micro analysis of the thread tooth surface and fracture surface, and the results show that the main reason of high-strength bolt fracture is related to the thread defect, which generates large stress concentration, and both stress concentration of crack tip and corrosion condition in the open air cause the stress corrosion cracking.To figure out the reasons for the failure of high-strength bolts used in bridges, the researchers carried out a series of studies. First, the spatial and temporal distribution characteristics of failed high strength bolts in the Chaotianmeng Bridge were analyzed, then representative failed high strength bolts samples were selected and the causes of the failure of these samples were discussed from the perspectives of chemical composition, micromorphology of fractures, metallographic structure and mechanical property analysis. Based on the investigation of the atmospheric environment in Chongqing in recent years, the corrosion solution to simulate the humid climate of Chongqing was designed. The stress corrosion experiment, the electrochemical corrosion experiment and the corrosion fatigue experiment of high-strength bolts in the simulated humid climate of Chongqing were carried out. In this study, the effects of temperature, pH and concentration of simulated corrosion solution on the stress corrosion behavior of 20MnTiB high-strength bolts were studied through mechanical properties test, the macro and micro analysis of the fracture surface and the surface corrosion products.