Abstract: In order to study the fracture law and engineering value of the main roof plate structure under the condition of long side coal pillar (goaf).the main roof plate structure mechanical model considering the width and bearing capacity of long side coal pillar and the elastic-plastic softening characteristics of solid coal is constructed. The fracture position.sequence and shape of the main roof above the long side coal pillar area and solid coal area are comprehensively calculated and investigated. Compared with the traditional model from six levels and three regions.this paper expounds the new conclusions and significance of this model. The conclusions are as follows. ① The width and bearing capacity of the long side coal pillar can significantly affect the principal bending moment and the fist fracture sequence of the main roof above the solid coal area.but have little impact on the location of the main roof fracture line above the solid coal area (elastic zone.plastic zone and elastic-plastic boundary zone). The long side coal pillar can also significantly change the fracture position state of the main roof above the coal pillar area (three types).and with the increase of E and h of the main roof.the support coefficient kcm and width Lcm of the long side coal pillar.the plasticization range Lt-s.plasticization degree ks-0.solid coal foundation coefficient ktt of solid coal and working face width Ld decrease. Its evolution mode is that one continuous long straight line+short arc at both ends\" type(CM-N)→ two adjacent symmetrical straight line + short arc\" type(CM-L)→two large spacing symmetrical short arc\" type (CM-D). ② There are five types of location characteristics of the main roof fracture line above the long side and short side areas of solid coal. With the increase of E and h.when Lt-s,ks-0,ktt and Ld decrease.the evolution law is as follows:the long side and short side fracture lines are above the plasticized coal body area→the long side fracture line is above the elastic-plastic boundary area of coal body.and the short side fracture line is above the plasticized coal body area →the long side fracture line is above the elastic coal body area.the short side fracture line is above the plasticized coal body area→the long side fracture line is above the elastic coal body area.and the short side fracture line is above the elastic-plastic boundary area→both the long side and the short side fracture lines are above the elastic coal body area. ③ There are three types of overall fracture modes of main roof.and with the increase of E and h.and with the decrease of kcm.Lcm.Lt-s.ks-0.Ld and ktt.the evolution mode is as follows:Asymmetric width=37,height=22,dpi=110-X\" type of→asymmetric width=36,height=18,dpi=110-X\"→asymmetric width=38,height=21,dpi=110-X\" type. Aiming at the three kinds of mechanical models for studying the fracture of the main roof plate structure with long side coal pillar (goaf).the key differences of the models are compared from six levels.and its engineering value is expounded from three areas ( long coal pillar area.short side area and long side area).