Abstract: According to the powered support jamned accident frequently occurred when the concentrated coa ilas were inthe goaof the room and pllar miningin the shall w depth and close distance seam in China western mining area, based on the fully mechanized coal mining face in Shigeal Mine of Shendong Mlining Area as the object.the theoreical analysi and the numeical sinulaton method were applied to analyze the powered suppor jammed mechanisom.The resuts showed that wih the suppor of the concenrated oom an illar mining type coal ilas the top seam roof were completed.Before the ruly-mechanized coal minin face was under the areaof the top seam concentrated coa illars and when the coal mining face was under the areaof the top seam concenrated coa oilla area.the rof pressuecf te fally-mechanized coal mining face was normal asically and was less affcted to the powered suppots. Nhen thefrlly-mechanized cal fce was pushed foward andpassed through certain ditance under the concentrated illa area,the goaf of the rll-mechanized mining face was under the concentrated coal ilar area and therof staus would be changed from the elastc -lastic status to the ful astic statu . with the subsidence of the under burden rock.the rock insteailily nd falre were occurred and the large area fallure and subsidence of the top roo strata were ocured. The basic roof could not fom a stable ariculted rock beanm'structure. when the basicro was broken and intability ransiently occured ,a super dynamic mine prssurefar higher than the working res itance of the powered suppot was fomed and jammed the 80 % of the powered supporis aplid in the ully mechanized coal mining face. Therefore,the top suspended and yet notalen basc roof withthe instaility and roof cutting could not form a stable structure and would be the root causes of the large area powered supports jammed 'transiently.