Abstract: Variations of code pseudorange observations of BeiDou satellites in inclined geosynchronous orbit (IGSO) and medium earth orbit (MEO), lead to systematic deviation in code-phase combination observations. The one-step method based on single-difference between epochs, is proposed to modify the above errors, and the corresponding correction model has also been given. It is shown that, comparing with the existing modeling proposed by Wanninger et al, the final optimized models in this paper using one-step method can improve the stability of Melbourne-Wübbena (MW) observables of all IGSO/MEO satellites with the proportion of 23.88% on average. It is worthy to mention that C08 satellite performs the most remarkable improvement with the proportion up to 32.26%.