ε-HNIW coated with melamine-formaldehyde resin was prepared by in-situcondensatesation polymerization from ε-HNIW as the core material , melamine and formaline as wall materials. The coated ε-HNIW was characterized on structure, morphologies, thermal properties and impact sensitivity. It showed that ε-HNIW was well-coated and the sensitivity was reduced as the H₅₀ increased by 10.3 cm. The optimum reaction conditions are as follows: the mole ratio of melamine to formaldehyde was 1∶2.5, and the pH of preparing prepolymer and in-situcondensatesation step are respectively 8-9 and 4-5, the temperature of in-situcondensatesation step is 70 ℃.