Since the broken phenomenon is always appeared in the roof of mine roadway, it largely affects the roadway’s roof stability. With Material Mechanics theory, the authors expound bolt tail subjected to no center load action and roof bolt broken mechanism while roadway is supported with bolts. By theoretical analysis and Lab test, the paper puts forward a kind of new type bolts which may prevent bolt tails from being broken, bolt construction structure’s pattern, and bolt made technology. It is illustrated that the reasonable grading relationship between bolt body’s iameter and bolt tail’s screw diameter. At same time, the authors compare disturbed values of the thick tail metal bolt and common bolt under the load action. It is verified that roof bolt broken problem may be solved with new type’s thick tail bolt. Therefore, the new type bolts have a wide application in the future.