This paper presents a security assessment method for intelligent distribution transformer terminal unit（TTU）. Facing the applications of management and edge computing of distribution station area，the main security problems faced by the terminal are analyzed，and the key system indicators affecting the terminal security are extracted. Based on the mathematical model of information entropy，a stochastic forest mathematical model for terminal security situation assessment is constructed. By constructing a simulation example，the evaluation method is validated by the stochastic forest model. The results show that the proposed method can accurately identify and classify terminal anomalies，thus realize security situation assessment，and has a certain practical value.