Abstract: The pulley rope system is a type of multi body system that can be controlled by ropes embedded within it , generally, there are a large number of contact segments,with the complexity and intelligence of mechanical systems, high demands have been placed on the accuracy and reliability of such systems . This paper mainly focuses on the space pull rope contact section of the nuclear ring lifting mechanism. Firstly,the equilibrium equation of the element body of the rope in the contact section is derived, and the analytical expression of the contact force density is obtained. Secondly,the solution of rope strain is transformed into an optimization problem.The nonlinear equation of strain and arc length derivative of strain is established by using Kuhntak condition. The derivative of internal strain to parameters at both ends of pulley is obtained. The strain distribution in contact section and the coordination equation between azimuth Angle and arc length are calculated. At the same time, the relationship between tangential and normal contact force density is derived based on the geometric characteristics of the pulley groove section, and the boundary conditions that the rope on both sides of the pulley should meet are proposed. Based on the condition that the material velocity of rope and pulley at the boundary point is equal, the constraint equation is established. In this paper, the contact forces of pulleys with different radius and different types of pulleys are analyzed, and the strain distribution rules of the contact section are summarized.The numerical examples show that the calculated results are consistent with the law of stress deformation and the trend of contact force change of the rope. The method presented in this paper provides a new idea for the analysis of large-scale mechanical systems including pulley and rope mechanisms. Moreover, it also provides theoretical preparation for the analysis of pulley-rope systems.