The present invention relates to a marine radar echo simulation system and particularly provides a DEM data superposition-based marine radar echo simulation method. The method comprises the steps of A, reading the electronic sea chart data of a target region, storing a contour in the form of a linked list, storing the position information of a guide control center in a radar simulator, and transferring the information in a GPU constant register at the same time; storing the DEM data of the region in a GPU texture buffer; B, invoking a preset timer function in a Microsoft development library; C, responding to the information of a timer to generate user-layer data, and conducting the radar plotting. According to the technical scheme of the invention, the processing speed of a marine radar simulator is improved. Meanwhile, the simulated radar echo simulation accuracy is improved.