Hydrogen fuel cell engine low-temperature operation method and system

The invention relates to the technical field of hydrogen fuel cell engine low-temperature operation, and discloses a hydrogen fuel cell engine low-temperature operation method and system.The method comprises the following steps that S1, a hydrogen fuel cell engine receives a starting instruction, and the cooling liquid temperature T1 at a cooling liquid inlet of an electric pile and the cooling liquid temperature T2 at a combination valve are detected; the T1, the T2 and a cold start set threshold T3 are compared, if the temperature of any one of the T1 and the T2 is lower than the T3, the step S2 is executed, and otherwise, the step S4 is executed; s2, an inner circulation loop and a combination valve heating loop are started, T1 and T2 are detected, and the step S3 is executed until T1 and T2 are both larger than T3; s3, a heater of the inner circulation loop and a combination valve heating loop are closed, and the step S4 is executed; and S4, starting a low-temperature cold start process of the hydrogen fu