A new kind of areated foam mud technical system unused air compressor was first discussed in the paper. It adopts to the complex drilling with its low density, high viscosity and low filter ation loss in the conditions of low pressure, lost circulation, hole wall unstablity, dry and leacking water. Its many fine characteristics have been shown about shear thinning, cuttings transportation, lubricating and resistance reduction, hole wall maintenance, loss prevention through our research. In this paper, we present formation and quality of foam, lubrification,rheology, cuttings removal and polluttion prevention (ion or temperature etc. ) from the preparation of new type DF foam agent, optimum formula, evaluation of rheological parameters etc.,and put forward a series of drilling technology of areated foam mud and surface equipment. The great technical and economical benefits have been achieved in the geological drilling, water well drilling, oil and gas drilling, geothermal drilling and engineering geologic drilling.In addition, we first set up new view points on mechanism of hole wall maintenance and loss prevention through the research of microstructure of filter cakes of foam mud. It is that it prevents the invasion of free water and lost circulation through wellbore wall because of the action of adsorption and grouping of stable foam on wellbore and adsorption layer of foam with the advantage of hydrophobicity, viscoelasticity and barrier of foam with phasefacies and grouping strneture.