In this paper, the realizing principle of the digital single-chip microcomputer fuzzy controller (SCMFC), which is based on the FFSI, has been presented. Then the developing principle of the hardware and software of the SCMFC 80C552 and some technical mains have been discussed in detail. The SCMFC will be a bridge to apply the theory of the fuzzy logic reasoning in the HVAC systems and equipments.