Aiming at the contradiction between the capture speed and the capture accuracy of fine acquisition of GPS signal, a GPS fine signal acquisition method based on orthogonal search is proposed. The code phase is firstly removed according to the coarse acquisition result of the GPS signal, and then a set of non-orthogonal sinusoidal candidate functions is constructed according to the coarse capture result of the frequency and the coarse capture resolution. Finally, Gram-Schmidt orthogonalization method is used to achieve the fine acquisition of frequency. Experimental results show that the frequency acquisition performance of the proposed method is better than that of the commonly used zero-filled FFT method, which balances the contradiction between capture speed and capture accuracy and is suitable for current mobile navigation and positioning equipment applications.