Boiler is one of the key industrial equipment in the field of modern manufacture. Rule-base reasoning (RBR) and case-base reasoning (CBR) are first applied to the boiler conceptual design. The RBR is adopted to perform like a “sieve” for the acquisition of the candidate structure modules. Then the CBR process is adopted for the structure module modification and case retain. The case retain process gives the system self-enrich function which will improve the design ability of the system with the continuous use of the system.