The invention provides a sealing mechanism used for a packer type liner hanger, which comprises a feeding tool, a sealing shell 23, a tie-back cylinder 4, a packer and the like, wherein the sealing shell 23 is provided with a plurality of through holes and internally provided with a safety chock block 24; and the inner wall of the tie-back cylinder 4 is provided with an annular shallow groove 44 on the position corresponding to the safety chock block 24. When a back-off nut 21 in the feeding tool is tightened with the sealing shell 23, one end of the safety chock block 24 is squashed into the annular shallow groove 44, so that the feeding tool, the sealing shell 23 and the tie-back cylinder 4 are connected into a whole through the safety chock block 24 to prevent the advanced sealing in the process of running a liner. A sealing short node 6 in the feeding tool and the outside of a sealing sleeve 11 are sleeved with a protecting hydraulic cylinder 10, and a sealing chock block 12 is protected in the protecting hydraulic cylinder so as to prevent that the sealing chock block is accidentally ejected out and sealed in advance in the process of lifting the feeding tool after loosing backing off, to prevent the sealing chock block from scratching the inner wall of the tie-back cylinder at the same time, and to solve the problem existing during sealing the packer in the prior art.