The semi-analytical（SA) approach is proposed for the fast determination of gravity field from GOCE observations，the first Core Mission of ESA's Living Planet Programme，which strives for the determination of a high-accuracy and high-resolution global gravity field model. Based on the application of FFT and introduction of the nominal orbit（circular，exact repeat orbit，uninterrupted measurement time series，and constant inclination)，the SA approach can recover the potential coefficients from large observations in short time. This method can give a fast diagnosis of GOCE system performance in parallel to the running of GOCE mission by comparing the estimated noise characteristics of the SGG time series with the gradiometer error PSD（prior). The performance of this method is evaluated using the simulated observations of the different cases（ideal and practical). The results in this paper show that this method can be applied to the practical cases of non-circular，non-repeat orbits and non-constant inclination in the time series of observations by the iteration algorithm，which can eliminate or weaken the approximation errors in the observation model. The test examples show that for the recovery of the high degree gravity field model，the optimal regularization parameter should be selected in the Kaula regularization technique.
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