Due to the weak signal power of GPS(Global Positioning System), GPS receivers are vulnerable to radio frequency interferences. Various antenna array processing techniques have been researched to mitigate the effect of the interferences. However, antenna arrays are usually too heavy and bulky to be applied to small platforms. This paper proposes an interference mitigation technique using a dual-polarized antenna, which consists of RHCP(Right Hand Circularly Polarized) and LHCP(Left Hand Circularly Polarized) antennas. Polarization characteristics of incident signals and the dual-olarized antenna are taken into consideration and the optimal weight vector is calculated using MVDR(Minimum Variance Distortionless Response) algorithm. Computer simulations are provided to show the interference mitigation performance of the proposed algorithm.