In order to measure the light environment of the ships navigation at night better, so as to lay the foundation for the evaluation of the light environment of the ships navigation at night and reduce the impact on the safety of the ship's navigation at night, a method of measuring the brightness of the sea light environment by a color CCD camera was proposed. Based on the principle of imaging, the relationship between brightness and camera parameters was deduced and the chromaticity calibration experiment was used to fit the relationship between the three-stimulus value and the standard RGB. The brightness calibration experiment fits out the unknown parameters in the formula and then the brightness measurement formula was determined. The port of Dalian Newport cruise terminal was chosen to verify the measurement formula. The results show that the method can measure the brightness of the light environment of the ships navigation at night, which has high precision.