Abstract: The thyristor model provided by common electromagnetic transient simulation software ignores the reverse turn-off characteristics of thyristor, resulting in inaccurate simulation of commutation failure of the thyristor converter. In order to improve the simulation accuracy of thyristor valve, we established a effect relationship of zero-crossing current change rate, positive current peak and junction temperature on the reverse recovery current peak, reverse recovery charge and turn-off time of thyristor turn-off characteristic parameters. Meanwhile, we proposed a characterization method of related influencing factors in device modeling, and established a custom digital simulation model of thyristor including reverse blocking recovery process and forward blocking recovery process.Moerover, we constructed a refined electromagnetic transient model of the converter considering the turn-off characteristics of the device. The comparison between the simulation results and the actual test values shows that the simulation error of the reverse recovery current peak is less than 5%, and the simulation error of the turn-off time is less than 4%. The proposed digital simulation model can accurately reflect the turn-off process of the thyristor.The converter simulation model can more accurately reflect the commutation failure characteristics of HVDC system.