Abstract: The paper analyzed causes of "9?8" especially serious gas explosion disaster at No.4 Coal Mine of Xinhua District which led to death of 76 people: amount of high-concentration gas accumulated in 201 tunnelling roadway because of roof caving which caused blowing-out of local ventilator of 201 tunnelling roadway; peccant air supply caused gas concentration to explosion limit; cable of coal electric drill of 201 tunnelling roadway lost explosion-proof ability to ignite gas; coal dust participated in explosion. Then it summarized accident lessons: the mine had confused ventilation management, such as small roadway section, thick coal dust, serious air leakage of air door and series ventilation of outburst mine; the mine used wooden support which caused serious roof caving; the mine had confused electromechanical management, such as underground cables had torn shield, electrical equipments lost explosion-proof ability, and maintenance of integrated protectors of coal electric drill did not accord to regulations; the mine did not implement regulations of lock between gas and electricity and between air and electricity; local ventilator had no special power supply and no other ventilator standby; sensors in safety monitoring and control system of the mine were far less than requirements of relevant standards and regulations, and were neither installed in correct sites and nor properly used; when safety monitoring and control system alarmed, the mine took wrong actions with pulling out sensors to avoid supervision other than cutting power and evacuating people. At last, it pointed out that gas control must be done in various aspects of ventilation, monitoring, drainage, power supply, explosion-proof, dustproof, fireproof, blasting and risk avoiding.