Abstract: Electric heating is an important practice to reduce fluid viscosity in wellbore for waxy crude field. Therefore, it is challenging to optimize the electric heating parameters with fluid flowing in annulus. Through transient heat transfer model based on Hasan-Kabir’s equations, a new numerical simulator was built to model such a multiphase, multi-heat sources production system including an inner annulus inside tubing as the electrical able installed, and an outer annulus where the gas is injected. This model and application for gas-lift assisted wells were presented. The results indicate that the new model is able to simulate the multi-interface heat transfer under transient condition. The presented model not only satisfies the exceptional modeling requirements for periodically-heating crude producers, but also it is appropriate for other heat transfer investigations under transient multi-interface and multiphase flow condition.