Modeling of the maritime environment lays a foundation for path planning at sea. For this reason, a nautical chart binarization method based on a pixel matrix is put forward with a grid model and discretization. Red-green-blue images were obtained by adopting the imread function in Matlab software, while the rgb2gray function in Matlab was employed to convert these red-green-blue images into grayscale images, so as to gather the exclusive pixel information. By extracting the pixel information of navigable sea areas, grayscale images were directionally transformed into a binary nautical chart. Based on actual needs, grayscale images could be transformed into red or black to achieve the binarization of the nautical chart.