Plasticity indexes (PI) of clay bodies including bottom ashes (BA) and various wastes by using Atterberg limits were measured for the effective recycling of coal bottom ashes from the power plant. Coal bottom ash (BA)-red clay (RC or simply clay), dredged soil (DS)-BA, coal fly ash (FA)-red clay, DS-FA were used as samples for the PI measurement. From the comparison of clay bodies with BA and DS, PI of DS-BA body was higher than that of BA-red clay body because liquid limit (LL) was high and plastic limit (PL) of DS-red clay was low, respectively. Comparing clay bodies with FA and BA, PI of BA-clay body was higher than that of FA-clay body because both LL and PL of BA-clay body were low. When stone ashes and sewage sludge (SS) were added to BA-clay bodies, PI decreased with increasing both stone ash and sewage sludge contents. It is concluded that the measurement of plasticity index can be used as an indicator of forming performance of green bodies with various compositions.