Design method of expanding type anti-sticking packer

The invention relates to a design method of an expanding type anti-sticking packer substituting for a lower packer connected with an original construction pipe column, belonging to the field of oil and natural gases. The design method of the expanding type anti-sticking packer is characterized in that a preloaded spring, a pressure relief hole I and a pressure relief hole II are arranged on the lower packer, a rubber drum is clamped on the inner wall of a sleeve to be used as a stress support point of the packer when the packer is not contracted, and a central pipe downwards displaces relative to the shell of the packer so that the pressure relief hole I is communicated with the pressure relief hole II, therefore the pressure difference inside the packer is eliminated; one end of the preloaded spring is pressed below an upper joint, and the other end presses on one end of an upper pressing sleeve in a supporting way; a sleeve of the preloaded spring is positioned on an upper transition sleeve; the pressure relief hole I is arranged on a pipe wall positioned on the upper ends of lower joints; and the lower joints positioned at both sides of the pressure relief hole I are provided with sealing rings II. The invention solves the problems of drill pipe sticking accidents caused in such a way that the lower packer is not unsealed during separate-layer fracturing construction.