The natural gas is the cleanest fuels in the world. Because of its liquid phase, It meets the energy saving benefit on vehicles energy supply. In order to improve domestic emission, the Environmental Protection Department in Taiwan build the Liquefied Nature Gas emission verification platform to verify the emission on vehicles DDF conversion from the domestic industry apply. By interviewing industry、collecting global promote policy and relative regulation，the workable subsidize draft could be researched for Environmental Protection Department reference. Regarding to the regulation field，The project has proposed recommends for modifying regulation in the future. One company has applied this project to test diesel engine from conversing DDF. From the test result, it shows PM and NOX value decreased after conversing DDF, except 250 times THC value and 3 times CO value increase . It’s no significantly emission decrease overall. This result has the same trend with United State's DDF vehicles test. From economic evaluation, The cost to converse DDF is NTD1150000 per vehicle which is higher than salvage value. It affects the willing for the owners to converse the DDF. From the emission decrease performance comparison from in-use vehicles converse DDF and new vehicles with LNG，it shows lower performance of DDF converse to new vehicles with LNG. Since LNG vehicles are mature products globally with good customer service and quality guarantee，the price is closer to diesel vehicles，It is suggested that dedicated LNG vehicles can be first target and plan a long-term strategy to prompt.

Natural Gas Vehicle;Liquefied Nature Gas;Applying Benefit Assessment