Objective To establish a new trajectory tracking algorithm combined with trapezoidal velocity, so as to realize the trajectory control of the assistive standing-up robot and help subjects complete the standing-up training. Methods Forces of the assistive standing-up robot acting on subjects were analyzed by deducing the force and moment balance equations. According to the interpolation points of the target curve, trapezoidal velocity and current position points of the end-effector, the trajectory tracking algorithm of the assistive standing-up robot was developed, and a simulation platform was built up by Simulink/Stateflow software. Based on the established Xpc target and host computer, assistive standing-up robot and 3D motion analysis system, trajectory tracking of the straight line, curves in different shapes, standing-up curve of the subjects were tested. Parameters that affected the velocity and accuracy of trajectory tracking as well as the differences in trapezoidal velocity and standing-up velocity were discovered. Results Accurate positon control of the assistive standing-up robot was achieved by trajectory tracking algorithm. The standing-up trajectory curve and trapezoidal velocity could meet the requirement of standing-up velocity for the subjects and fulfill their requirements for different curve shapes and velocities. Conclusions The assistive standing-up robot using trajectory tracking algorithm combined with trapezoidal velocity can accurately track the target curves without limitation of curve shapes, and help the standing-up training for subjects. The established simulation and test platform in consideration of different subjects’ standing-up trajectory curve, velocity and accelaraion will assist standing-up more effectively.