Abstract: In order to optimize the advantages of FTA evaluation method and LEC evaluation method, the two evaluation methods were analyzed and studied, and the FTA-LEM evaluation method was proposed. Firstly, the LEC evaluation method was improved, and the risk severity (C) was changed to control measures (M), LEM evaluation method was proposed and the respective variables and the score of risk (D) were presented. Secondly, the identification of risk source and the specific method of normalization of risk score were expounded. Then the risk score was optimized by calculating the critical importance in the quantitative analysis of FTA.The normalization method of risk score after optimization was proposed, and the steps of the FTA-LEM evaluation method were listed.Taking the poor ventilation of coal mine ventilation system as an example, by using the FTA- LEM evaluation method, the risk score of each hazard source in the poor ventilation accident was evaluated and calculated, the evaluation results can provide theoretical basis for safety management of ventilation in coal mines.