In order to reduce the difficulty in the ranging of monocular marine images and improve the degree of information mining of marine images,a monocular ranging method is proposed.Based on the sea-sky line detection and pose-calculation monocular ranging technology,the camera pose is calibrated by using the sea-sky line in the image,and the external parameters of the camera are obtained.In combination with the cameras internal parameters calibrated in advance,the model describing the geometric relationship between the target and the camera in the imaging space is constructed.Considering the influence of the Earths curvature,a real-time monocular marine ranging method based on sea-sky line calibration is deduced.Finally,the Monte Carlo method is used to simulate the ranging model and analyze its error characteristics.