Aimed at the problem that because the result zone algorithm is in search of space by adopting the method of traversing all attitude angles, the initialization time is comparative long,an improved planar ambiguity searching method is proposed based on the combination of narrow lanes. First, based on the relationship of satellite space geometry to restrain the narrow lane ambiguity scale between reference star and two main stars, all the candidate attitude angles can be obtained by using the relationship between the attitude angle and the narrow ambiguity, thus obtaining the searching range in a way neither traversing nor missing the correct candidate. And then, each corresponding narrow-lane ambiguity float solution is derived from result zone planar searching model. and the narrow-lane ambiguity is fixed by using ambiguity integer characteristics method, baseline length constraint method and least square sum of baseline residual. The experiment results show that the new method can effectively reduce the initialization time from 153 s to 76 s and the attitude accuracy invreases nearly by 15% comparing with the original algorithm.