Leakage currentamplitude of lightning arrester is affected by ambient weather conditions. The model of leakage current is significance for health diagnosis of lightning arrester. In this paper, a model of leakage current of lightning arrester is established with multiple linear regression and ambient weather analysis. Firstly, the factors effect on the leakage current is collected. These factors include ambient temperature, humanity, atmospheric pressure and light intensity. Then, the factors are analyzed by using scatter diagram and trend line and the multiple linear regression model of leakage current is given with the least square. This proposed model is diagnosed with the varianceinflationfactor. Finally, the proposed model is used to predict the leakage current of lightning arrester for next ten days. The predicted results show that the proposed model have high accuracy and can be used in actual engineering.