A system and method are outlined for controlling and optimizing chemical injection into a process unit to control fouling. The method uses an optical device to measure the fouling propensity of the process fluid at various points within the process unit. The measurements are compared with one another and prediction methods are used to evaluate the fouling potential within the unit, and determine the proper chemical dosage. Antifoulant chemical is then introduced into the unit to control the rate of fouling. The method and application continue on a frequent basis to maintain optimal fouling control within the unit.