Crosswise, length wise and moving stability of ZY9000 / 24 / 58 two-leg shield large mining height hydraulic support was analyzed, vertical anti-dumping stability factor was taken as example, changing law of anti-dumping stability coefficient was concluded by analyzing the change of working face angle, the changing of maximum column active force along with the change of working angle in support with pressure moving was analyzed. The result showed that support height, working face angle, axis space, centre of gravity place and other parameters affected the stability of support, the corresponding measures of improving the stability of large height mining support were given.