To analyze the cost effectiveness of GHG mitigation technologies for the participation enlargement of the voluntary GHG reduction project in korea, this study made use of the KVER(Korea Voluntary Emission Reduction)project data. KVER project has been designed by MKE(Ministry of Knowlege and Economy) in 2005 and performed under the MKE rule. The major data for cost effectiveness analysis are total investment cost of mitigation technologies, energy saving cost, amount of GHG reduction. All these resources are gained out of the output of KVER project from 2005 to 2010. Originally, we expect that financial burden of the companies participating in the KVER project would be high but the results of GHG reduction cost come up against original expectation. The main reason why we got unexpected results is due to the effects of energy saving cost. Especially, 78% of KVER projects are no-regret project owing to the cost benefit effect and mitigation technologies for heat energy and electric energy are favorable in terms of cost effect. Henceforth, dissemination of these technologies would be very useful for the accomplishment of our country`s GHG mitigation target in the law of low carbon & green growth.