Multipath frequencies need to be estimated for tide level inversion from Global Navigation Satellite System Reflectometry (GNSS-R) signals.However,conventional inversion methods only estimate principal frequency,which results in low data utilization and insufficient temporal resolution of the inversion results.Here,we use the Savitzky-Golay (SG) smoothing filtering to optimize the GNSS-R tide level inversion.First,the Lomb-Scargle Periodogram (LSP) is used to extract the first four frequencies (f₁-f₄) of signal power,which are then inverted for their corresponding tide level values.Then the SG smoothing filtering is used to extract the best inversion results.Finally,the 30-day data from BRST and MAYG stations in France are used to verify the effectiveness of the approach.The results show that,compared with LSP method,the proposed approach increases the number of daily average inversion values by 34.3% and 19.6%,and reduces the maximum time interval of inversion values by 43.2% and 29.4%,for BRST station and MAYG station,respectively;compared with window LSP (WINLSP) method,the proposed approach increases the number of daily average inversion values of BRST station and MAYG station by 24.2% and 45.9%,decreases the maximum time interval of inversion values by 25.4% and 28.6%,respectively,and reduces the RMSE by 7 cm for both stations.It can be concluded that this method increases the number of inversion results,raises the data utilization and improves the temporal resolution of tide level inversion besides adequate accuracy.