The invention relates to a method of determining transformer forced air cooling full cut-off by using transformer cooler load current. The method comprises steps that (1) transformer forced air cooling power supply inlet wire current is acquired, and working current of every group of a draught fan and an oil pump is acquired; devices used for measuring current are disposed on the transformer forced air cooling power supply inlet wire and the circuit of every group of the draught fan and the oil pump, and are used to input acquired current values in a transformer forced air cooling control device; (2) when the acquired current value of the transformer forced air cooling power supply inlet wire is equal to the sum of the working current values of the various groups of the draught fans and the oil pumps, normal working continues; when the acquired current value of the transformer forced air cooling power supply inlet wire is zero, and the working current values of the various groups of the draught fans and the oil pumps are zero at the same time, full cut-off occurs. The forced air cooling full cut-off determining is carried out by adopting a way of determining the analog quantity of the transformer forced air cooling power supply, and various defects caused by adopting a way of determining the forced air cooling full cut-off only by using a contactor are solved.