The temperature and humidity were found to be the most effective parameters in the behavior of polyurethane flexible adhesive bonded aluminum joints. In order to obtain the effect of environment on bond strength, toughness, failure displacement, joints stiffness and failure model, in this work, aluminum single-lap joints were tested under various temperatures (25, 40, 60 and 80 degrees C) and relative humidity (RH, 55, 65, 75, 85, 95 and 99%) using an environmental chamber. The results showed that as the humidity increased from 55 to 99%, bond strength decreased as linear function. As the temperature increased from 25 to 80 degrees C, the bond strength decreased as exponential function. The joints stiffness reduced gradually with the increase of temperature and humidity. The analysis of the failure section of the ageing joints showed that the humidity caused the transition of the failure model, and the increase of the temperature promoted the change of the failure model. Besides, at low humidity (55 and 65%), failure displacement decreased gradually with the increase of temperature, and at high humidity (95 and 99%), failure displacement increased. This study will help engineers design a reliable, safe and effective bonding structure. And it is conducive to solve the problem of joint strength degradation in the hygrothermal environment.