Important information such as amplitude, frequency, phase and polarization was encoded in the interference pattern. One important phenomenon that has not been studied in detail is the interference of two Gaussian beams with any polarization state. It is necessary to find a relation between polarization of light and interference pattern. In this paper, a fiber Mach-Zehnder interferometer was used to produce light with spatially varying polarization. A general expression for the light intensity distribution is derived for interference of two Gaussian beams with arbitrary polarization. The theory is validated by experiment. The research shows that various interference patterns can be generated as the polarization is changed. Two Gaussian beams with the same polarization states can interfere and clear interference fringes were observed. Two Gaussian beams with orthogonal polarizations can not interfere and no interference fringes are observed. In other cases, the fringe contrast varies between 0 and 1. This study is very helpful in understanding and applying the interference of polarized light.