Abstract: Under-balanced drilling has the advantage of improving the drilling rate, reservoir protection, outstanding advantages of oil and gas reservoir, but the ground water gushing and borehole instability have seriously impeded the generalization of under-balanced drilling. The conventional methods of Wall-Protecting And Leakage-Plugging can not meet the requirement of gas drilling technique any more; on the other hand, the introduction of chemical grouting technology will become an effective way to solve the technical problems. Chousing the formamide as hardening agent, the gelation action of sodium silicate and Formamide in high temperature has been analyzed. The research has got a new chemical grouting material which characterized by high temperature resisting, well groutability, controllable gelation time under high temperature and high compressive strength of consolidating body. It can be used for gas under-balanced drilling in the complex formation of wall-protecting and leakage-plugging.