Abstract:In order to optimize the CDM development and co-control the air pollutants, the air pollutant reduction co-benefits of CDM were assessed. All registered projects of China (host country) in EB(executive board) were classified by category(zero emission renewable, biomass, waste gas recovery, fossil fuel switch, fugitive, cement, N2O and energy efficiency) and location(Central, East, Hainan, North, North East, North West and South) according to their annual reduction, total investment and cooperative emission reduction coefficient. Cooperative emission reduction and investment benefits of SO2, NOx and PM2.5 were calculated. The project types of fossil fuel switch, fugitive and energy efficiency showed high investment benefits of emission reduction, while the gains of wind and hydro power projects were low, generally. Biomass projects in Central and East China revealed higher income of reduction.