In order to solve the problem of low efficiency and manual operation of flame photometer in the process of soil and plant sodium content detection and analysis，a method of sodium determination by combining flame photometer with continuous flow analyzer was built. The content of sodium in soil and plant samples was determined by this method，and the detection conditions were optimized. The results showed that the concentration of sodium was linear within 10 mg/L，the correlation coefficient was 0.999，and the relative standard deviation was less than 3.12%. The detection limits of sodium in plant and soil samples were 0.018 and 0.016 mg/L，respectively. In this research，the high degree of automation of continuous flow analyzer and the high detection accuracy of flame photometer were combined，and the rapid and accurate determination and analysis of soil and plant sodium content were realized. At the same time，the new functions of the instrument was expanded.