Aiming at the technical problems such as damage tendency and collapse tendency during drilling process in coal bed reservoir section，a new microfoam drilling fluid system with low-damage and high-performance was developed. The gemini anionic foaming agent（LHPF-1），zwitterionic foaming agent dodecyl dimethyl betaine（BS-12）and biopolymer thickener（XC） were compounded. The interaction between the three treatment agents on the comprehensive foam index was analyzed by using response surface optimization experiments. On this basis，the filter loss reduction agent and inhibitor were selected to determine the best formula of microfoam drilling fluid. The comprehensive performance of microfoam drilling fluid was studied. Finally，it was applied on Laochang exploration area in east Yunnan. The results showed that the best formula of microfoam drilling fluid was obtained as follows：0.25% LHPF-1，0.25% BS-12，0.25% XC，1% brown coal resin，1% polyacrylonitrile，0.2% potassium polyacrylate. The density of drilling fluid was 0.49 g/cm³，the foaming volume could reach 420 mL，and the half-life of foam could reach more than 33 h. The thickness of foam film reached 50% of the foam size，and the sealing rate and permeability recovery value of the core of coal seam were above 90% ，while it could resist 7% of rock chips and coal dust pollution. In the field application of drilling fluid，the drilling time was 4 days without any downhole complications. The average enlargement rate of well diameter was 5.9% in the whole well section，and the filtration loss was less than 5 mL. The microfoam drilling fluid had good rheology，rock-carrying，inhibition，plugging and reservoir protection effects.