This paper presents a new heuristic algorithm for implementing fast service restoration based on analytically index in un-balanced distribution networks. A suitable assignment of switch indices to all tie switches (ts) in networks are used to find best solution and decrease number of switching operation. Customer’s priority, load variation and minimum out-of-service loads have been considered in this paper. Three levels for load demand have been considered to load variation. The validity of this approach has been tested on the one un-balanced three phase distribution networks. Results have been presented for modified IEEE 37-node test case. The fastness and effectiveness convergence of this approach helps finding best solution for service restoration problem.