Abstract: Biodiesel is one of the best alternative fuels. Research status of emission NO_X of diesel engine with biological diesel from four aspects was summarized in the paper. The reason of NO_X emissions increase were discussed, and the measures of reducing NO_X emission were analyzed from two aspects, i.e., the improvement of biodiesel and diesel engine. Further research direction was pointed out.

Key words: diesel engine, bio-diesel, emission, NO_X