The utility model discloses a substation main transformer temperature measurement circuit fault detector, and relates to the technical field of substation maintenance. The detector comprises an adjustable resistor, a resistor R1, and a multi-meter, wherein the adjustable resistor and the resistor R1 are parallelly connected and then connected with a temperature transmitter; and the multi-meter is used for detecting resistance or two-end voltage of the adjustable resistor, and detecting two-end voltage of the temperature transmitter. According to the substation main transformer temperature measurement circuit fault detector, main transformer temperature measurement fault detection can be conveniently carried out, a fault point can be directly positioned, the fact that a worker climbs a transformer for live working due to inaccurate fault point can be avoided, the possibility of live working can be reduced to the maximal degree, and the safety factor of field work is greatly improved.