In order to discriminate the top coal caving of 8202 fully mechanized caving face, the variation law of ultrasonic velocity and the influence of crack distribution on ultrasonic velocity were analyzed, and the mechanical model of caving coal caving was established. Combined with the specific situation of the working face, the model was used to analyze the caving of the top coal in the working face, and the accuracy of the predicted model points was verified by field measurements. The results showed that the top coal in the 8202 fully mechanized caving face was good in caving, the prediction model with higher accuracy.