Thermally expandable micro capsule (TEM) can be expanded upon heating since activation energy of liquid hydrocarbon at the core of the TEM is increased under high temperature. These properties can be used to application of the plastic foaming process. In this study, thermally functional expandable micro capsule (F-TEM) was designed for controlling curing time and temperature of epoxy resin. F-TEM was prepared with a mixture of the liquid hydrocarbon and the epoxy curing catalyst in the core and polymeric compositions for the shell. Since F-TEM was designed for having thermally vulnerable polymeric shell, catalyst in the core could be released at the designated temperature and time. Therefore, F-TEM does not activate in epoxy resin at room temperature but only functions while epoxy resin is cured at high temperature. This study contains the results depending on the different composition of liquid hydrocarbon and catalyst. It was confirmed that the curing time and temperature of epoxy resin can be selectively adjusted depending on the ratio of liquid hydrocarbon to catalyst in the core. The F-TEM was studied as the functional additive for epoxy resin which can be applied for carbon fiber reinforced plastic to reduce the automotive weight.