Hydrophilic, solid, powdery diammonium bitetrazole (BHT.2NH(3)) as a fire retardant was microencapsulated with epoxy resin by the method of in situ gelation in droplets to give water resistance. In this method, a nonaqueous solvent was adopted as the continuous phase instead of water to prevent the hydrophilic core material from leaking out. In the experiment, it was mainly the agitation speeds during preparation of droplets containing BHT.2NH(3) and during the microencapsulation process, the gelation temperature, and the oil-soluble surfactant species that were varied. The content of core material could be increased by using a non-aqueous solvent instead of water phase. The content of core material increased with gelation temperature and independently of the agitation speeds during first droplet preparation and during the microencapsulating process. The leakage ratio increased with agitation speeds and decreased considerably with gelation temperature.