A lifting electrical push rod mechanism which is suitable for the upper load pitch lifting has been designed based on a particular mobile radar in this paper. Through the theoretical modeling analysis of the lifting force of the electric actuator and the stability of the screw during the whole Lifting process, this article aims to investigate the influence of the compound load on the force and stability of the push rod during the lifting process of the screw, and to verify the accuracy of the calculation results by combination with the actual measurement results. The research results show that: in the lifting process of the upper load from the lifting angle 0 to 90°, the self-weight moment of the upper load is the main influencing factor of the force on the electric push rod, and in the lifting process, the maximum force on the electric push rod appears in the middle state of the lifting process, the lifting angle with the most dangerous screw stability coefficient and the position of the maximum force on the screw do not overlap. In the lifting process, the measured results and the theoretical calculation values are in good agreement, which proves the accuracy of the calculation model and method.