In order to know the stability of the temporary horizontal ore pillar during sim ultaneously mining in more than one level in Jinchuan No.2 mine,according to the stress characteristics of the horizontal pillar the mechanics model for it were proposed. On that basis,the total potential energy expression of the horizontal pillar was derived out by the analytical method of catastrophic theory,the cusp catastrophic model for predicting the failure of the horizontal pillar was set up,and the necessary and sufficient mechanical conditions leading to the active earth pressure were presented. It was concluded that the failing probability of the pillar is small.For the safe recovery of the pillar,some engineering measures were given.