Oil and gas well leakage is a common problem in drilling， usually sealed with cement. However， the heavy weight of ordinary cement can easily lead to failure in plugging. Meanwhile， low-density cement has been rapidly promoted in plugging. The compatibility between low-density cement and retarders is particularly important， which the performance of cement is effected seriously by retarders. In response to the above issues， a retarder for low-density cement. The infrared and thermogravimetric results indicated that the preparation of the retarder has achieved ideal results， with a temperature resistance of 450℃. The test results of the high-temperature and high-pressure thickener showed that a retarding time of 225 minutes was obtained for the low-density cement with 0.4% retarder under the conditions of 120℃ and 68MPa， which is a good retarding effect. By using a six speed viscometer， thickener， and unconfined compression tester， the effect of retarders on the conventional performance of low-density cement slurry was studied. The experimental results confirmed that different concentrations of retarders did not have a significant impact on the rheological properties and compressive strength of cement， and an increase in temperature would shorten the thickening time of cement slurry. The prepared retarder has been applied on site together with low-density cement， and the on-site results have shown that the retarder has excellent effects and meets the needs of on-site construction， which is worthy of further promotion.