Abstract: Differential Code Bias is also called instrumental bias,and is one of the main error sources affecting PNT services. GPS instrumental bias is usually solved with ionospheric model coefficients. However, BDS method is now a regional satellite navigation system, which is difficult to obtain precise instrumental bias results using only BDS itself. In this paper, we propose a means to estimate BDS satellite and receiver instrumental biases using combined GPS/BDS observations in spherical harmonics modeling. The precision of BDS satellite instrumental bias was about 0.3 ns using this method, and the GEO/IGSO satellite instrumental bias precision was more stable than the MEO satellites. Besides, the precision of the satellite instrumental bias is better than receiver instrumental bias.