It is required that conventional instrument control system should be rebuilt in the atmospheric-vacuum distillation unit in the petrochemical enterprise. Current situation in communication signal category between all kinds of sensors and input devices in the control room was described. Adapting to development that computer control technique is widely used to automation system of petrochemical enterprises, industrial IT Freelance 2000 DCS was adopted to implement production process’ automation controlling of the atmospheric-vacuum distillation unit. According to practical needs of units and safety and stabilization requests of system, DCS’s software and hardware frame were determined. A configuration control plan, which advanced computer control algorithm was applied to the typical control loop of the unit, was described. Finally, installation request for DCS was given. The system can reduce error and promote control precision.