A relay service life detection device includes a controller unit, L on-off counting units, a human-machine interface unit, a relay drive unit, and an oscillator unit, and can simultaneously count thenumber of on-off times of a plurality of relay switches to obtain on-off count values and determine whether the relay and the switch thereof are faulted according to the on-off count values. Anti-pulse interference circuits in the on-off counting units can filter out the edge jitter interference and narrow pulse interference in count pulses, and ensure the accuracy of relay service life detection.Multiple counters are disposed outside the controller unit to count the number of on-off times of the relay switches. The number of relay switches that detect the service life of the relay is not limited by the number of counters in the controller unit.