In order to reduce the diurnal in TWSTFT (two-way satellite time and frequency transfer), based on the fact that there is no diurnal in BeiDou common view link, the Vondrak-Cepek combined filtering was applied to combine BeiDou common view and SATRE (satellite time and ranging equipment) TWSTFT or SDR (software-defined radio) TWSTFT among NTSC (national time service center), Chinese Academy of Sciences, PTB (physikalisch-technische bundesanstalt) and NIM (national institute of metrology). Two indexes, namely time deviation and amplitude spectrum, were used to evaluate the gain factors in reducing the diurnal of the fusion results, and the agreement of the two types of links was revealed by taking GPS PPP (precise point positioning) time comparison as reference. Results show that the diurnal of the fusion results is greatly improved after Vondrak-Cepek combined filtering, and the absolute value of the differences between the fusion solutions and GPS PPP solutions is kept within the calibration uncertainty of time link. For the baseline of NTSC-PTB, the gain factors of 1-day time deviation(TDEV) of fusion results versus SATRE TWSTFT and SDR TWSTFT are 1.85 and 1.81, respectively. For the baseline of NTSC-NIM, the gain factors are 1.69 for SATRE TWSTFT and 1.59 for SDR TWSTFT. The short-term stability of fusion results is significantly improved.