Zhang Zhongjing′s theory system was analyzed by propositional logic correlation method from the aspects of the proposition of “Without Obstruction Is Harmony” and taking “the unobstructed” as the logical starting point. The corpus was selected from the Golden Chamber, with the application of hypothetical proposition forms and its methods of reasoning, interpreting and refactoring the contents, so as to illustrate the theoretical thought of “Without Obstruction Is Harmony” from Zhang Zhongjing′s treatment. It is found that Zhang Zhongjing always regarded “Without Obstruction Is Harmon” as his treatment principle. He was aimed at eliminating pathogenic factors so as to dredging qi, blood and meridian, and finally to achieve the goal of human health. And the necessary and sufficient condition for proposition that Zhang Zhongjing always followed is that if and only if there is “no obstruction”, then it is “Harmony”.