Morden GNSS has adopted the new navigation, such as BOC，MBOC and AltBOC etc. The performance of BOC modulation is better than BPSK modulation. However, auto-correlation function (ACF) of BOC modulated signal has the multiple side peaks due to subcarrier modulation. So, it is difficulty in acquision and tracking for BOC modulated signal, especially in multipath propagation. In this paper, based on analyzing the ambiguous problem of BOC, a novel unambiguous correlation technique is developed. Finally, the validity of the proposed algorithm is verified through computer simulation. Research results can be used to guide the implementation of unambiguous tracking for BOC signals.