In this paper, we calculate the flow in an aircraft vapor-core pump that has been designed and manufactured in recent years. The physical and mathematical model of gas-liquid two phase flow are subjected by analyzing the flow,well known SIMPLE algorithm is used, but modified properly. The numerical method as well as the computer program that can be used in rotating two phase flow are presented. Results of numerical simulation are In agreement With our experiments, with difference less than 13-19%. The method is hopeful for two or single-phase flow calculation of other rotating systems.