Coronal plug is a key component of the horizontal deepsea tree, and its main function is to block the tubing hanger and tree cap, thus preventing the oil or gas from leaking upward. During the step-by-step installation process of deepsea tree, the installation of the crown plug is an important part of the whole process. The mechanical installation of the coronal plug needs special installation tool, the analysis of the mechanical behavior of the coronal plug installation tool is directly related to the underwater installation successful rate and difficulty degree of the coronal plug. This article mainly aims to analyze the Mises stress of installation tool claws in the process of unlocking the coronal plug tool. The stress and displacement distribution of the claws at different stages of the unlocking process is obtained by Abaqus FEM(Finite Element Method) software. According to the FEM results, the author analyzes the stress distribution law detailed and improves the claws model and it has been validated that the maximum stress of the claws is greatly reduced. The article plays a guide role for the design of the coronal plug installation tool.