Exfoliation of pitch coke particles treated on 1000 and 3000°C was tried via electrolysis in nitric acid and following abrupt heating to 1000°C. Although apparent evidence for intercalation of nitric acid was not clearly observed in potential change during electrolysis up to an electric charge of 1000C and also X-ray diffraction pattern of the sample after electrolysis, the particles of 3000°C-treated coke showed exfoliation, where small pores with relatively homogeneous sizes, 30μm×10μm, were formed by cleaving between hexagonal carbon layers. The exfoliation behavior was supposed to be strongly governed by certain structural constraint which kept the coke particles shape and hindered the intercalation of nitric acid.