Based on the 16 years of data collected from the TOPEX/Poseidon and Jason-1 nominal ground tracks during the primary mission, and six years of TOPEX/Poseidon and Jason-1 interleaved ground track data, we calculate the system error in the South China Sea using the synchronous observation period data. This includes 2 184 primary ground track normal points and 1 626 interleaved ground track normal points with the difference of latitude of 0.1°. Harmonic analysis of the primary normal ground track points, and response analysis of the interleaved ground track normal points, was performed to acquire eight tidal constituents of the harmonic constants, including Q1, O1, P1, K1,N2, M2, S2, K2. Internal accuracy assessment used the discrepancy in the junction points between the ascending and descending orbits. The results show that the interleaved orbit junction points have poor RSS quality of about 7.28 cm. A comparison with the global ocean tide models, shows that the results obtained in our study have a similar performance as the tide models in the South China Sea, except for a big difference RSS quality in the semi-closed shallow-water areas. A comparison with the gauge results shows that the northern part of the South China Sea have poor RSS values due to the influence of the complex tide-wave system. The RMS value of the M2 constituent in the results reported in this paper and the tide models were 13.64 cm, and the rest of the tidal constituents were within 10 cm. © 2018, Research and Development Office of Wuhan University. All right reserved.