Abstract: A surgical planning scheme for robot-assisted celiac interventional therapy system is proposed.Through analyzing the surgical procedure,a physical model is presented to simplify the needle into an operation arm with a single globe hinge joint.The nonlinear equations with parameter are adopted to obtain the analytic description of the needle's workspace based on the study on the analytic description of the arm's collision-free reachable workspace boundary in robotics.The ribs and blood vessels in the abdominal cavity are described with third-order continuous differentiable super quadric surface equation.With numerical iterative continuation method,the unidimensional manifold of needle's collision-free reachable workspace boundary is solved,and the three-dimensional models are displayed with the Matlab toolbox.For the case that ribs and vessels exist in the abdominal cavity,the workspace boundary of the needle is successfully obtained.According to simulation results,the needle-insertion path will not collide with fraises such as ribs and vessels if the entry point is selected within the needle's workspace boundary.This paper provides an effective means for doctors to make successful surgery operation planning,solves the problem that the current system determines the entry point by doctors' own surgical experiences, and improves the efficiency and success rate of surgery.