Abstract: Observable-specific signal bias, a new type of code bias, is important for improving the positioning accuracy of BeiDou navigation satellite system (BDS). This paper compares the performance of OSB products released by the Chinese Academy of Sciences (CAS) and Wuhan University (WHU) based on the new BDS-3 frequency combination B1C/B2a at the MGEX station. It is found that the stability of the OSB products of CAS is generally better than that of WHU products and has an impact on the localization performance. The PPP experiments using CAS products have better pseudorange and carrier residuals than WHU products, and their localization accuracies are also slightly better than WHU products. Moreover, the use of OSB products can improve the PPP convergence time and get higher positioning accuracy more quickly. And the effect of OSB product fluctuation on the positioning performance is analyzed, and it is found that during the fluctuation of CAS product, its pseudo-distance, carrier residual, and positioning performance all decrease.