Abstract: Pseudorange code biases will influence high precision data processing in BeiDou navigation satellite system (BDS). Based on Melbourne-Wübbena(MW) combination, we have analyzed the effect of code biases on baseline resolution according to the code biases correction models and the residuals of double differenced wide-lane ambiguity of baselines, respectively. The results show that the influence of code biases on double differenced wide-lane ambiguity resolution with MW combination is gradually obvious as the baseline becomes longer. Moreover, the impact on the 300 km baseline may reach up to 0.36 cycles. In addition, the results suggest that the code biases of geostationary earth orbit(GEO) have great influence over both short and long baselines. For inclined geostationary orbit (IGSO) and medium earth orbit (MEO), the code biases have little effect on baseline solution when the baseline is within 300 km, however, the residuals of wide-lane ambiguity of partial satellites have obvious biases when the baseline is over 300 km. Furthermore, the fixing rates of wide-lane ambiguity of these satellites are lower, so we should take into account the influence of code biases on baseline resolution at this time.