The invention relates to the field of measurement technology, in particular to a vibration monitoring and diagnosing device based on oil film thickness, which is used on large rotating machines such as sliding bearings in thermal power plants, nuclear power stations, petrochemical enterprises, and the like. The vibration monitoring and diagnosing device is characterized by comprising an ARM microprocessor which is respectively connected with a signal processing circuit, a field programmable gate array (FPGA), a liquid crystal display (LCD), a secure digital (SD) storage unit, an operating keyboard, an RJ45 network port, a communication port, a FLASH memory and an random-access memory (RAM); an eight-channel vibration transducer is connected with the signal processing circuit; the signal processing circuit is connected with a signal acquisition circuit; and the signal acquisition circuit is connected with the FPGA. By using the vibration monitoring and diagnosing device, the oil film thickness, the shaft vibration amplitude, the tile vibration amplitude of the large rotating machines such as the sliding bearings, and the like can be monitored in an on-line manner, and resultant faults of vibration states of the rotating machines can be diagnosed on the basis of the oil film thickness.