The invention discloses a reinforcement method for the single event latchup resistance of a CMOS device. Neutron irradiation is carried out on the CMOS device; a displacement damage is introduced in the neutron irradiation; and a current gain of a parasitical bipolar transistor in an inverter of the CMOS device is reduced, so that P-N-P-N latchup is not generated. The reinforcement method is an external reinforcement method; processing steps to produce the device will not be increased; there is no need to redesign a device layout for the single event latchup effect; and complexity of an original system will not be increased. Thus, the fixed size of the device will not be changed, and a peripheral circuit will not be increased either.