Abstract: Scientific and reasonable early warning index system is the premise of accurate and reliable early warning of coal and gas outburst. Based on the two "four in one" comprehensive anti-outburst technology systems, the fault trees of coal and gas outburst were compiled, and the basic events of the fault trees were summarized and classified. According to the classification results, the early-warning index system framework of coal and gas outburst was designed from four aspects, including production system defect, objective outburst danger, defect of outburst prevention measure and hidden danger of outburst prevention management. On this basis, the relationship between early warning elements and coal and gas outburst was analyzed, and 52 early-warning indexes were designed and selected to establish the early-warning index system of coal and gas outburst. The establishment of this system can provide guidance and support for the research of early warning method, model and system.