Abstract: In order to promote the small and medium-sized enterprises to achieve clean development mechanism(CDM) and spread biomass gasifier, four tons of coal boiler transform improvement was studied as an example. Greenhouse gas emission reductions of biomass gasifier were calculated by using methodology AM0036 approved by CDM-EB, IPCC emission coefficient and related references. The results showed that CDM could play a good role in spreading biomass gasifier. Some suggestions on how to implement biomass gasifier were made for enterprises.