As a branch of engineering cybernetics, automatic control theory has been extensively applied to improve product, increase productivity and rationalize management. As a first try, this paper intends to adapt the principles of conventional control theory to the field of software process, and use them to define a requirement process control system, its dynamic and steady-state performance, and steps in designing, analyzing and improving such a system. Preliminary studies show that more requirements engineering (RE) process activities relating to measuring elements, including those in feedback compensation and organization support, need to be introduced, recommended and selected. The results of this research can be used to guide the establishment and improvement of RE processes, compare different requirement process solutions quantitatively, develop methods for evaluating benefits from process improvements, and structure the application of knowledge about RE.