The fault detection and diagnosis is very important for a security of control systems.By analyzing deeply on the relationship between changes associated with process variables and between the device failure

a diagnosis technique is presented for process fault based on the correlation coefficient in process variables.The process diagnosis function is defined for interrelated variables based on the correlation coefficient (correlation coefficient

multi-correlation coefficient

partial correlation coefficient) constraints

whether the involved devices and instruments are fault is estimated according to the correlation coefficient change variety.If a fault in device or system occurs

the correlation coefficient and the diagnosis function changes will be caused

the fault location and the failure equipments are determined by logic analysis for diagnosis function value.Finally

the validity of the method is verified with a distillation column practical engineering case.