The invention discloses a combined system and process for the harmless treatment of an organic waste gas. The system comprises a pneumatic emulsifying absorbing unit, a biofilter bed, a negative pressure draught fan chamber and a circulating water treatment tank, the whole combined system is distributed in a hierarchical way, the pneumatic emulsifying absorbing unit, the biofilter bed and the negative pressure draught fan chamber are sequentially distributed and are arranged above the circulating water treatment tank, and water flowing out from the pneumatic emulsifying absorbing unit and thebiofilter bed directly flows into the circulating water treatment tank. A paint mist (paint particulate) of an organic gas and a gaseous phase pollutant of a volatile paint solvent are absorbed and transferred into water (liquid) through the high-mass transfer pneumatic emulsifying absorbing unit and the biofilter bed, the paint mist forms a paint residue floating on the water (liquid) and is convenient to collect, the secondary pollution of the gaseous phase pollutants in the water (liquid) is eliminated through digestion and degradation of biological flora, the water (liquid) is recycled, sothat the purpose of the harmless treatment of the organic waste gas is fulfilled.