The catenation effect of the rope of the long-span hoisting robot is studied. Firstly, the kinematic and dynamic models of the robot were established by using the cable as linear model. Secondly, there is gravity in the cable, and the long span cable was catenary model, in order to solve the cable tension in the catenary model, the quadratic programming method was used to solve the optimal solution of cable tension. Based on the statics equation, wrench feasible workspace and wrench closure workspace of the hoisting robot were obtained. Finally, the simulation was verified by MATLAB, the simulation results show that wrench feasible workspace is smaller than wrench closure workspace. Comparing the cable length of the two models, the length of the first cable changes the most, the cable tension is small, and the cable self-weight cannot be ignored.