螺杆压缩机是一种工作容积作回转运动的容积式气体压缩机械。气体的压缩依靠容积的变化来实现，而容积的变化又是借助压缩机的一对转子在机壳内作回转运动来达到。
Screw compressor is a kind of positive displacement gas compression machine with working volume rotating. The compression of gas depends on the change of volume, and the change of volume is achieved by rotating a pair of rotors in the casing.
螺杆空压机基本构造：在压缩机的机体中，平行地配置着一对相互啮合的螺旋形转子，通常把节圆外具有凸齿的转子，称为阳转子或阳螺杆。把节圆内具有凹齿的转子，称为阴转子或阴螺杆，一般阳转子与原动机连接，由阳转子带动阴转子转动转子上的最后一对轴承实现轴向定位，并承受压缩机中的轴向力。转子两端的圆柱滚子轴承使转子实现径向定位，并承受压缩机中的径向力。在压缩机机体的两端，分别开设一定形状和大小的孔口。一个供吸气用，称为进气口;另一个供排气用，称作排气口。
Basic structure of screw air compressor: in the body of the compressor, a pair of mutually meshed helical rotors are arranged in parallel. Generally, the rotors with convex teeth outside the pitch circle are called male rotors or male screws. The rotor with concave teeth in the pitch circle is called female rotor or female screw. Generally, the male rotor is connected with the prime mover. The male rotor drives the female rotor to rotate the last pair of bearings on the rotor to realize axial positioning and bear the axial force in the compressor. The cylindrical roller bearings at both ends of the rotor make the rotor realize radial positioning and bear the radial force in the compressor. The two ends of the compressor body are respectively provided with orifices of certain shape and size. One for suction is called intake; the other for exhaust is called exhaust.