A new distributed equipment condition monitoring and fault diagnosis network system based on an RS485 field bus and an industrial ethernet was designed for the main drive system of a hot strip mill. The system structure and composition were studied. The following problems were resolved: communication of an intelligence data acquisition module with RS485 interface; communication between a server, clients and a light emitting diode; and point to point communication between a programmable logic controller and server. Realtime signals of 24 radial runout, 12 axial drifting can be synchronously acquisitioned and stored in a database. System operation is satisfactory and can be used to identify the causes of rolling mill halt and transmission slip brake, and to improve sheet metal quality.