Due to the special work condition of AWP, security and stability become important indicators of its performance. At present, there are problems such as impact and vibration when the arm descended luffing which is a serious threat to the safety of staff. So it has great significance to do research on the stability of aerial cage when the arm descending. Here, we take the Runshare boom lift as example:

　　First, About the Runshare arm luffing mechanism. We built the mathematical model of luffing mechanism ; The mapping relationship between luffing cylinder displacement and height of the working platform and the force status of luffing cylinder piston rod when arm luffing are researched. Curves that lay the foundation for researching on the stability of the arm, such as force on cylinder, height-displacement, are got through simulation.

　　Second, the working principle of arm luffing mechanism hydraulic system, we established the mathematical model of hydraulic system. Combining the arm luffing hydraulic system with the simulation results of mechanical system, influence caused by the characters and the control pressure style of balance valve, the characters of proportional control valve and loads on luffing mechanism's working stability are concluded. Projects improving running stability are put forward.

　　Third, Considering the influence that made by luffing mechanism and hydraulic systems on the boom running stability, AMEsim/ADAMS model of luffing system is built to optimize arm's running stability when declining. Compared with several projects, the optimization project used in this paper is proved effective.

　　Finally, the optimized system and original system are tested in real cage. The result shows that the theoretical research and simulation analysis in this paper is true.