Different thermal techniques are used worldwide to increase recovery from heavy and ultra-heavy oil reservoirs. The conventional techniques of thermal enhanced oil recovery methods, because of excessive heat loss are not effective for recovery heavy oil reservoirs or deep wells. One way to introduce heat to the reservoir in a controlled manner is microwave heating. Different experiences showed that the successful production by microwave heating strongly depends on the initial conditions of the reservoir, such as initial water saturation and water salinity. The criteria for these parameters to improve the performance of the method are not well known yet. In this project, different experiments were conducted to study the effects of the main parameters on the performance of enhanced oil recovery by microwave heating. A Teflon core holder packed with glass beads was designed to study the recovery of a heavy crude oil sample from an Iranian reservoir under microwave heating. The core was saturated by crude oil and water and the influences of operational parameters, such as heating time, salinity, and initial water saturation on wave absorption were tested. The authors' experiment showed that the main mechanisms for enhancing the oil recovery were gravity drainage and movement due to viscosity reduction.