Abstract： Based on the analysis of the current situation of crane limit protection system in “Hai Yang Shi You 116”, three optimization methods of limit protection system are put forward in this paper. Firstly, boom limit protection logic optimization is realized by adding proximity switch protection. Secondly, the optimization of limit bypass mode of crane boom is realized by modifying the PLC control logic to cancel the variable amplitude coercive function. Thirdly, bypass management optimization is realized by changing the bypass management procedure of crane signal. After optimizing the limit protection system of crane, the safety and stability of crane operation have been improved.