Abstract: This paper describes the surgical planning model and the virtual fixture(VF) approach to the robot-assisted celiac interventional therapy.We introduce the spatial motion constraint generation method for two categories of VFs,i.e.guidance VF and forbidden-region VF,as well as an integrated admittance control strategy.The controlled object is guided by the attractive potential field and reference direction,and avoids the obstacles,i.e.,ribs and intraperitoneal vessels,by the repulsive potential field,in order to assist the motion and localization of the interventional instrument.The stiffness of a virtual fixture can be used to adjust the degree of rigorousness of the spatial motion constraint.Simulations of a single VF and multiple VFs in the celiac 3-D environment are executed to verify the effectiveness of spatial motion constraints and control algorithms.The proposed approach is applicable to some similar teleoperation and human-machine collaboration systems.