Bio-cybernetics is a systematic approach of planning which focuses on the interlinks among the system components instead of scrutinizing the individual factor. Based on Bio-cybernetic thinking, Vester (1980) designed the interactive computer software, Sensitivity Model, as a tool for implementation. The main purpose of the paper is to articulate the philosophy of Bio-Cybernetic thinking and the application of Sensitivity Model to planning practice, including both logical and technical issues, in terms of a practical system model of the central area of Taipei.