In order to resolve the problem that is low precision, slow speed and time consuming, which come out when selecting by artificial. This paper developed an automatic selection machine of cylinder length, which use advanced PLC controller to take the place of conventional mechanical control type. Moreover, it employs synchronous controllable automatic loading and automatic material distribution mechanism, greatly improved control precision and efficiency. Save production cost due to use contacting sensors. Rotary disk type and feeding integral type design pattern reduce the complex of mechanism, and selection speed can reach 120-200 every minute, it realizes the purpose of accuracy and fast.