Aiming at solving the problem of using the two-way "Λ" configuration to achieve high-stability time-frequency comparison between the ground station and the low earth orbit spacecraft in near circular orbits, a new method for longer-term stability calculation was proposed. The method used the statistical characteristics of the short-term data to generate pseudo-measurements and fill the data gaps. The validity of the algorithm was verified using data simulated. To analyze the influence of spacecraft orbit determination error on time and frequency transfer, the Hill equation, the relative motion model in the time-transfer model and the relativistic frequency shift model were combined to analyze and calculate the requirements of orbit error for different long-term indexes. For long-term ps level stability indexes, the requirements of orbit error are that the radial and tangential errors are around 10 m, and the normal error is about 1 200 m. For long-term sub-ps level stability indexes, the requirements of orbit error are that the radial and tangential errors are around 1 m, and the normal error is about 120 m. The results shows that the error of the orbit determination is not the factor that limits the performance of satellite-ground time-frequency comparison to achieve 0.01 ps level short-term stability and sub-ps level long-term stability.