Abstract: With the rapid development and wide application of nuclear energy technology, more and more attention has been paid to the safety monitoring of marine radioactive environment. Due to its advantages of low cost, low power consumption, and high detection efficiency, the NaI(Tl) Gamma spectrometer has become the main application instrument for automatic and continuous monitoring of marine radioactivity. However, the detection resolution capability of this spectrometer is insufficient, which leads to difficulties in nuclide identification and quantitative detection. In order to solve this problem, this study adopts technical means such as theoretical calculation, simulation and experimental measurement to conduct research on the processing and analysis method of seawater Gamma spectrum based on inversion analysis. The results show that the resolution of the reconstructed spectral lines calculated through inversion analysis in the simulation experiment has been significantly improved. Compared with the reference values of the channel address and activity of nuclides in the simulated spectrum, the channel address errors of ¹³⁴Cs, ¹³⁷Cs,⁶⁰Co, and ⁴⁰K nuclide peaks in the reconstructed spectral lines are within 2 channels, and the calculation error of activity is within 4%. The results of in-situ seawater experiments conducted at the Marine Science Experimental Station in Qingdao showed that the activity analysis of ⁴⁰K nuclides using the inversion analysis method yielded a result of 1.218×10⁴ Bq·m⁻³. This method can effectively solve the problem of insufficient detection resolution of the NaI(Tl) Gamma spectrometer and achieve accurate analysis of radionuclides analysis in seawater.