The main objectives of this comparative study were 1) to compare the floristic similarity of species composition between the extant vegetation and seedlings from soil seed bank and 2) to quantify the potential contribution of soil seed bank to revegetation of forest in a constructed area, which is called "ecological impact mitigation" in conjunction with the power plant extension. Forest topsoil of seven plots was collected from the surface soil after measurements were taken on the ground vegetation in each plot. A greenhouse experiment was conducted and monitored to analyze the germination potential of soil seed bank. The forest topsoil was spread on plastic trays ($0.7m^2{ imes}7$) filled with a 5cm layer of sterilized potting mix. The results of monitoring for 2 years in a greenhouse were as follows : 1) seedlings of soil seed bank per 4.9$m^2$ were 1,269 with 36 species (1st year) and 2,615 with 25 species (2nd year). 2) 38${pm}$8% of the flora species were germinated from soil seed bank. It can be concluded that the use of soil seed bank would be effective to promote establishment of diverse species and vegetation. However, it behooves to continue monitoring on succession of vegetation and pursue revegetation with other methods for ecological restoration. Finally, adequate topsoil deposit and gathering methods should be studied properly.