The invention relates to an automatic coal caving system on a top coal caving working face and a coal caving method thereof. The automatic coal caving system comprises a monitoring host, support controllers, inclination angle sensors, distance measuring instruments and data acquisition devices, wherein the distance measuring instruments and the data acquisition devices are mounted on end hydraulic supports in top coal caving supports, and the data acquisition devices are connected with a scraper conveyor of the top coal caving working face; the support controllers are in the same number with the top coal caving supports, and each top coal caving support is provided with the support controller; the inclination angle sensors are in the same number with the top coal caving supports, and the inclination sensor is arranged on a tail beam of each top coal caving support; the monitoring host is mounted in an underground road and in wireless connection with all the support controllers; each distance measuring distance and the corresponding data acquisition device are electrically connected with the support controller on the same top coal caving support; and each inclination angle sensor is electrically connected with the support controller on the same top coal caving support through a connector.