Filter hardness is important to filter and cigarette manufactures because it is directly related to the ability of a plugmaker during making filter and to the acceptability of the filter by the consumer. In general, glycerol triacetate(Triacetin, TA) is the currently used common plasticizer in making filters from cellulose acetate tow and the effect of triacetin on hardness of filter which is made of mono cellulose acetate tow was well known. But unfortunately, the effect of triacetin on the hardness of cellulose acetate filter containing ativated carbon(carbon filter) was not reported so far. In this study, we manufactured filters with various carbon content at different triacetin concentrations and then analyzed the filter hardness and pressure drop. Filter hardness was directly increased with triacetin concentration but pressure drop was not affected and the effect of carbon content on filter hardness was smaller than that of triacetin concentration. However, pressure drop was directly increased with carbon content.