Abstract: The gas injection wells have been placed in many low-permeability reservoirs for oil displacement. The present release-type gas injection string is good for pipe replacement in later stage, solving the problems that a large amount of gas needs to be released and the well killing difficulty, when the Y211 gas injection string works again. However, in field test, problems occurred like poor packing setting and that release tools cannot be released. A new release-type gas-injection packer has been developed, which seats the rubber sleeve by both pumping liquid pressure through tubing and adding weight by lowering the pipe string, hence improving its sealing performance. Release can be realized hydraulically or mechanically by dropping ball, and later it can be tied back and sealed for gas injection. After the packer was designed, indoor simulation experiment and field test were performed, which show that the sealing performance of the packer is reliable, meets the onsite requirement of gas injection technology, extends the repair-free period, reduces the cost of gas injection and lays a good foundation for the promotion of drainage technology by gas injection and hence enjoys a promising application prospect.