Phase tensor is a very useful parameter, despite the impedance tensor, the phase tensor is independent of the distortion caused by shallow structures and it can providing information about the dimensionality of the geoelectrical structures by showing as ellipses. In this paper, phase tensor method was performed on the magnetotelluric data of Sabalan geothermal system in order to dimensional analysis and determining the geological strike. After needed processing and data rotating based on the phase tensor analysis, 2D inversion was done on the magnetotelluric data. The result of inversion successfully showed the geothermal reservoir and its cap rock and it has a good agreement with previous geophysical studies and wells information.