The real-time dynamic monitoring of water volume has great value for risk assessment, prediction, and early warning and disposal decision-making of dammed lakes. In view of the difficulty in obtaining underwater topographic data of dammed lake in areas without gauged data on the plateau, directly, quantitatively, and timely estimating the water volume of dammed lake by using remote sensing technology is difficult. This study aims to solve the problem of rapid quantitative estimation of water volume of plateau dammed lake under unknown underwater terrain scenario by remote sensing and perform the risk monitoring and disaster assessment of dammed lake.According to the existing remote sensing data and digital elevation information, this study puts forward a remote sensing quantitative estimation method of water volume of dammed lake on the plateau without underwater terrain by fully using remote sensing data. The details are as follows. First, the submerged area of dammed lake is extracted from remote sensing images. Second, the center line of the complex polygon of the dammed lake is calculated. Specifically, according to the water area of the dammed lake, the Tyson polygon algorithm is used to calculate the position information of the dammed lake centerline. Third, through the location of the polygonal center line of the dammed lake, the fixed-point elevation measurement is carried out to complete the fitting calculation. Then, according to the fitting estimation of the middle line elevation and combined with the slope elevation information, the unknown underwater terrain of the dammed lake is adaptively simulated. Finally, based on the simulated underwater terrain and the submerged area of the dammed lake, the capacity of the dammed lake is calculated by 3D curved surface space discrete integration.The dammed lake, namely, Sarez Lake in the Pamirs was selected as the research area. Remote sensing survey and empirical research on water volume were carried out using the proposed method. The research results show that the water area of Sarez dammed lake is approximately 89.09 km2, and the water volume of Sarez Lake is approximately 16.25 billion m3. This result is consistent with the expert’s estimated water volume of 15.5 billion m3 to 16.5 billion m3. The accuracy verification of the local simulation experiment shows that the overall dynamic error between the simulation data and the measured data is controlled within 10%, and the correlation coefficient is 0.95 (P<0.01, double tailed). This finding further proves the robustness of the algorithm and the credibility of the estimation results.This method can rapidly estimate the water volume of plateau dammed lake, with high accuracy and strong technical universality. It provides an efficient method for remote sensing estimation of plateau dammed lake water volume under none or lack of underwater terrain data scenario. It also solves the problem of quantitative calculation of plateau dammed lake water volume with unknown underwater terrain.