Elbow draft-tubes are widely used in largeand medium-sized hydropower stations in many countries.During the application,handling the somatotype of elbow tubes has been found challenging: in order to maintain the designed shape of draft tube and to meet the requirement of construction lofting,the configuration of reinforcing bars and the fabrication of templates,the geometry of elbow tubes has to be accurately calculated to draw engineering graphics.Based on the derived equations in this paper,the motion of elbow tube curve envelope is simulated by using computers,which shows directly the smoothness of the curve and provides dynamic simulation for the study and optimization of the design and construction of elbow draft tubes,along with the front view and bottom view. Elbow draft-tubes are widely used in large and medium-sized hydropower stations in many countries. Driving the application, handling the somatotype of elbow tubes has been found challenging: in order to maintain the designed shape of draft tube and to meet the requirement of construction lofting, the configuration of reinforcing bars and the fabrication of templates, the geometry of elbow tubes has to be accurately calculated to draw engineering graphics. Based on the derived equations in this paper, the motion of elbow tube curve envelope is simulated by using computers, which shows directly the smoothness of the curve and provides dynamic simulation for the study and optimization of the design and construction of elbow draft tubes, along with the front view and bottom view.