The conventional line-of-sight (LOS) geo-location method using two-dimension interferometer on a satellite leads to heavy payloads and it is always under the effect of amplitude phase inconsistencies among receiving channels. A novel passive localization method is proposed, which merely needs two receiving channels to form a one-dimension interferometer on a spin-stabilized satellite. Rate of phase difference change was measured for emitter localization. A location algorithm based on particle swarm optimization (PSO) was designed. The impact of rotating speed and rotating plane of the interferometer on localization precision was analyzed. The results showed that localization precision can be improved by increasing rotating speed of the interferometer, the rotating plane should be perpendicular to the satellite position vector at the initial moment in order to get good localization precision in all directions around satellite projection point on the ground, and localization precision of the proposed algorithm can approach the Cramer-Rao lower bound (CRLB).