Total Organic Carbon（TOC) refers to the total carbon content of the organic substances dissolved and suspended in water, which is a comprehensive indicator for the total amount of organic substances in water. The traditional measurement technologies of TOC arethe national standard combustion method and the wet chemical method, which always involves complicated test methods, long measurement time, slow speed, some atmospheric environment, and can only be completed in the laboratory and not available to the seawater online in-situ measurement. The concentration of TOC in seawater is measured with ultraviolet absorption spectroscopy technology using the optical in-situ sensor developed by our research team, which achieves online in-situ quick measurement of TOC without adding reagents, doesn’t induce secondary pollution, and is not restricted by the laboratory environment. In this paper, the sensor developed by our research team is used to real underground seawater TOC measurements for different sea areas (the sea area around Huanghua Portand Qinhuangdao City, in Hebei Province), and comparison of correlation, consistent and measurement error between sensor measurement method andnational standard method is conducted, which shows that: The evolution trend of the concentration of TOC from the 13 different seawater samples in the Huanghua Port area and the 14 different seawater samples in the area around Qinhuangdao obtained using TOC optical in-situ sensor are basically consistent with that obtainedfrom the national standard method. Better linear correlation and consistency is demonstrated, and there are very few water samples that deviate from the overall sample curve. The experimental data shows a good correlation through the linear fitting, and the data fitting curves and conventional error are analyzed for two different sea areas. The correlation coefficient of the linear fitting for the water sample of Huanghua Port is r=0.859 0, and the sum of squared residuals is 0.165 4. The correlation coefficient of the linear fitting for the water sample around Qinhuangdao is r=0.939 9, and the sum of squared residuals is 3. 5131. Because the correlation coefficient r=0.939 9>r=0.859 0, which means that the linear fitting effect of water samples around Qinhuangdao is better than that of Huanghua Port experiment. The conventional error is 0.165 4<3.513 1, which is caused bymore serious pollution induced by some samples around river estuaries in Qinhuangdao city. Domestic sewage and industrial wastewater induce more interfering factors in water quality, which cause certain influence to the accuracy and stability of marine TOC optical in-situ sensors; TOC in-situ optical sensors based on ultraviolet absorption spectroscopy technology and traditional methods are different from the national standard method, which uses smaller sample set and sample concentration coverage, however, the marine environment is complicated and changeable, and the sensor cannot completely avoid the influence of all other factors, such as turbidity, temperature, PH, plankton, etc., which is the main source of the measurement error. The future exploration is how to eliminate the influence of complicate interference factors in the marine environment, reduce the error of sensor measurement values, make the measurement results more accurate and true.