The invention discloses an accumulation test method and system of a network switch delay of an intelligent substation. The method comprises the following steps: step 1: a test device obtains a self loop inherent delay t1; step 2: the test device tests a tested device to obtain a delay t2 of the tested device to forward and receive a preset message; and step 3: the test device obtains a forwarding delay t3 of the tested device, and calculates to obtain the exchange delay of the tested device t = l t3-(t2-t1) l, and the technical effect of less accumulation test loss of the exchange delay is realized.