In　terms　of　three　factors:　static　equilibrium,　strength　failure　and　fracture　failure　are　both　related　and　different,　and　all　act　on　working　surfaces　of　rock　bursts,　and　through　the　study　about　fracture　mechanics　of　two　computing　models　on　rock　bursts　＇　tunneling　faces,　this　paper　determined　the　mechanical　mechanism　and　critical　conditions　of　rock　bursts　and　gave　a　quantitative　explanation　for　the　general　regularity　of　rock　bursts　occurrence.