The structure of oil-less air compressor is shown in Fig.1 & 2. All units in the machine sit on a cylindrical pressure vessel called air tank. Compressor machine is main part of the air compressor, A motor drives directly the eccentric wheel-connecting bar system making the piston move reciprocally. The piston is made from high temperature resistant and abrasion resistant non-metal material and is able to work without lubrication for a long time. Compressed air discharge enters in the air tank; a pressure meter displays the pressure in the tank. When the pressure inside rises to 8 bar, power is automatically cur off by a pressure control switch, the compressor is shut off. When the pressure inside lowers to 6 bar, power is turned on by the pressure switch, the compressor starts again and the pressure in the tank gradually rises again.This happens repeatedly. The high quality compressed air can be supplied to dental therapeutic instrument. In addition, check valve, drain valve, safety valve are installed on the air tank.