To explore the influence of BDS-3(BeiDou navigation satellite system phase Ⅲ) different frequency combination satellite DCB(differential code bias) on PPP(precise point positioning), the BDS-3 different frequency ionospheric-free combined satellite DCB correction model was derived and performed DCB correction experiments by seven different dual-frequency combinations based on the observation data of four MGEX stations during seven consecutive days. The results show that the DCB correction has a significant improvement of the PPP accuracy in the initial epoch, which helped to converge the filtering and improve the RMS of the single-day solution, but weakly in the final positioning accuracy. Although the positioning accuracy of the B2a/B3I and B2b/B3I combinations′ convergence speed are considerably thinner than other combinations, it still enhances after DCB correction. Otherwise, the positioning accuracy and convergence time of the other 5 combinations are equivalent after correction. The RMS of the static PPP single-day solution is about 5.50 cm, 2.50 cm, and 6.25 cm in the E, N, and U directions, which are approximately 20%～65% higher than before. The average convergence time, an increase of about 6%, is 38 minutes. And the kinematic PPP, an increase of about 20%, is 59 minutes. The final positioning accuracy is better than 5 cm in the horizontal component and 7 cm in the elevation component.