In the paper a new hierarchical two-level structure of the control system for extrusion process is presented. In the system the inferior direct control level stabilizes the zones temperatures utilizing conventional algorithm. The superior level is an optimizing one and it determines the zones set temperatures with the aim to stabilize, independently of the extruder productivity: the quality of plastic expressed in terms of degree of thermal degradation, degree of homogenization and the plastic final temperature, It draws on heuristical mathematical models that describe the effect of extrusion on plastics characteristics. The performance of the new control method is examined by simulation techniques.