The bolt joints on cage guide are difficult to monitor their loosening state,usually periodic inspections by artificial are conducted at the cost of time and money.However,it is very difficult to check whole bolts in-site carefully.In order to improve this situation,an effective method is proposed to detect the bolt loosening which used RFID(Radio Frequency Identification Devices)technique.The main principle of the detection system is that the metal film can influence the data communication between the RFID tag and reader.