The geological conditions in the Guangdong Heyuan area are complex with well developed karst caverns and fissures. Drilling difficulties usually lead to serious circulation loss, long construction period and high cost. A new type of polymer gel plugging agent was developed to cope with the local formation with large size caverns and fractures. Theoretical analysis is made of the basic performance and the mechanism of the new type gel plugging agent, with lab experiments and field tests conducted on the gel forming time, load bearing capacity, breaking performance, etc. Comparative tests were done on different gel formula, resulting in an optimum make-up which was applied to plugging with good performace, such as reducing consumption of the drilling fluid, increasing the drilling efficiency. Application in the Guangdong Heyuan area shows that the new type gel plugging agent provides liquidity with the short gelling time, meeting the field needs; meanwhile it can also bear high load, and offer significant gel breaking performance, eliminating pipe sticking. The new type plugging agent was very effective in the Guangdong Heyuan area, and featured of easy concoction and without adding any special equipment. It will find promising application in areas with large size caverns and fractures.