In the surgery of nasopharyngeal cancer, the surgeon operates through natural channels within small room. In its robotassisted surgery, collisions between two manipulators and parameter variation of local tissue may lead to contact force change, It may cause target position offset. As the vessels and nerves were distributed densely in head and neck. The control system needs to ensure the operating contact force is within the safety threshold. It can avoid soft tissue tearing caused by changing of relative position over the limits. The research studies indirect adaptive admittance control based on position synchronization, which adjust the damping compensation rate. It improves the force control precision and system robustness of robot-assisted surgery through alleviating the effect of stiffness variation and collisions. And it can improve surgery security.