Working environment is one important factor to equipment failure. In order to quantity the environment influence to equipment failure, this paper qualitatively analysed some environment factors’ effect to equipment failure and drew the graphs about the relationship between equipment failure and environment factors. Based on bathtub curve principle, progressively increasing curve and Weibull distribution principle which are basic theories in reliability engineering, this paper built a mathematical model about environment influence to equipment failure and put forward a calculating method to the unbeknown parameters in the model.