Based on the rough set theory, this paper introduces a multilayer rough-fuzzy rules design method to keep fuzzy rules dimension of every layer not more than three for consistency with man's thinking characteristics, advantageous for understanding, checking and correcting rules. For rationally reducing and integrating input variables, the paper presents a rapid fuzzy rules extraction algorithm based on RST, to discover knowledge from sample database. This algorithm improves C-D indiscernible matrix. It introduces the computation program for core attributes. The program for quasi-optimal attribute reduction is presented, in which information increment of decision D is used as heuristic information of attributes selection to accelerate selective velocity of optimal attributes set. This multilayer fuzzy controller is combined with conventional PID, applied in unit control system of power plant. The simulation results show that the control system has higher control qualities with high speed, small overshoot and strong robustness.