Hydration reaction characteristics of a composite of calcium chloride and silica microcapsules with nano-holes were investigated. Silica hollow microcapsules with holes were fabricated via a double emulsion method, and calcium chloride was inserted in the capsules. The properties of the cell were compared with those of calcium chloride/expanded graphite treated in a previous study. The hydration reaction experiments show that the reaction rate was considerably higher than that of the composite of calcium chloride/expanded graphite at the initial stage. This was because of the high thermal conductivity and the low contact thermal resistance between the composites and the heat transfer plates of the present cell. Further the power of the present composite cell was 9.78 times greater than that of the expanded graphite because the proposed capsules contains a larger amount of calcium chloride. Thus, the present composite is a promising item not only for realizing the chemical heat pumps but also for the machine start-up heating.