Abstract: In order to overcome the shortcomings about a large amount of calculation and strong subjectivity of the present top coal cavability evaluation methods, the authors established a new top coal cavability evaluation method which was easy to calculate and promote. The paper analyzed the major impact factors of top coal C avability, and assigned weight value to those factors. Based on extension theory evaluation criteria, a extension theory model of evaluating top coal cavability was establ ished. The practical results showed that the new top coal cavability evaluation model would have the advantages of simplicity in calculation, reliability of predicted result s and practicability in site.