In order to consider the influences of induction motors with pump loads on the static voltage stability of distribution networks more accurately, a load model of an induction motor is established, which combines the T-type equivalent circuit of induction motors with the mechanical characteristics of pump loads. The model is incorporated into the power flow computation of distribution networks, then the back/forward sweep method is used to solve the power flow. Furthermore, the proposed load model is adapted for Continuation Power Flow (CPF), and an equivalent load model of a number of identical induction motors with pump loads is deduced, the load model is used to analyze the effect of continuous load growth on the static voltage stability of the distribution networks. IEEE 33-bus test system is used to verify the proposed model and method, and the results are compared with the ones acquired with the CPF method with constant power factor load mode. The simulations verify the validity and effectiveness of the proposed method, and show that the static voltage stability margin with the load model proposed in this paper is less than that with the constant power factor load model, the proposed load model is more approximate to actual engineering conditions. This work is supported by National Natural Science Foundation of China (No. 61473002) and Special Project of State Grid Sichuan Electric Power Company (No. 521909160001).