Nowadays, more and more global navigation satellite systems (GNSS) start to provide more than dual-frequency observables. Multi-frequency observables will contribute to precise data processing. However, this will also introduce a new type bias, named as inter-frequency clock bias (IFCB). In this paper, four-order Fourier function is employed to fitting the GPS and BDS IFCB. Based on the characteristics of four-year data, we established empirical correction model of GPS and BDS IFCB. The results show that correction models in this paper can greatly decrease the effect of IFCB and improve triple-frequency precise point positioning accuracy.