Aiming at the problem of the isolated coal pillar occurring the rock burst easily and having no the occurrence and damage theory of the rock burst according with actual, it discusses the generation mechanism of tension rock burst of the isolated coal pillar, uses finite element software of the tension fracture to simulate the fracture and evolution process on the function of the triangle load of the isolated coal pillar. The result shows that the coal pillar generates tension fracture on its both sides, the fracture direction is horizontal. After the coal pillar cracks, the stress is released, forms new stress concentration and the loose region. The coal pillar generate to slide on the horizontal direction on the interaction of the coal pillar and the top and bottom roof and on the function of the geological. This can provided the theory basis for the prediction and forecast of the rock burst of the isolated coal pillar.