The invention provides an industrial network detecting system time synchronization method. The method comprises that a measuring node Rn in an industrial network detecting system is randomly designated to a main node, and a measuring node neighboring to the main node firstly issues a clock synchronization request to the main node and records an issuing time t1; after receiving the clock synchronization request, the main node feeds the self clock value T back to the measuring node; the measuring node receives the feedback value T, records a receiving time t2, and according to a formula of T+(t2-t1)/2, updates the value of a self counter to achieve time synchronization between the neighboring measuring nodes and the main nodes; then the others measuring nodes sequentially achieve clock synchronization with the main node. As required, the others measuring nodes except the main node issue the clock synchronization requests to the main node every at set intervals, so that the clock synchronization requirements among the measuring nodes during long-time measurement can be improved. The industrial network detecting system time synchronization method can achieve consistency of time of the Rn and the others measuring nodes and obtain a time synchronizing precision up to the ns (nanosecond) level.