Abstract:The instability and failure of strip coal pillar along strike is a typical nonlinear process. A mechanical model of strip coal pillar is established,based on which,the expression of total potential energy function is derived. Then the cusp catastrophic model for instability and failure of strip coal pillar along strike is set up by catastrophic theory. The formula of necessary and sufficient condition for instability and failure of strip coal pillar along strike is obtained according to the cusp catastrophic model. In the mean time,the effect of underground water on the coal pillar is considered in the model for the first time. The cusp catastrophic model indicates that underground water reduces the strength and the rigidity of core part of coal pillar and leads to sudden instability of coal pillar. At last,the mechanism of instability and failure for strip coal pillar along strike is analyzed according to the cusp catastrophic model. As a result,a new theoretical method of studying the instability and failure of coal pillar of strip-partial mining is put forward.