At present，the domestic caliper logging tool adopts an eccentric circular arc type in the pushing arm， which has the problems of large dynamic load， poor force transmission effect， and short instrument life. In order to solve the above problems， the three kinds of structural schemes of involute， Archimedes spiral and eccentric circular arc are used for parametric design of pushing arm， and the three kinds of pushing arm cam motion characteristics and mechanical efficiency are analyzed. The analysis shows that adopting the involute pushing arm structure in the split pushing system can greatly improve the force characteristics of the piston rod， reduce the friction and wear， and further improve the measurement accuracy. The ADAMS/View module is used to create three types of split pushing systems to open and measure models， the initial parameters are set and motion simulation is performed. The trajectory curves of piston rods in three motion states are obtained， and their motion laws are verified， which provides a theoretical basis for the optimal design and performance improvement of the structure of caliper logging tool.