The structuring of fiscal affair theory system should abide by such principles as systematic completion, consistent logic, all-inclusive, scientific practice and dynamic stability. The environment of conducting financial transactions is the basic absolute category for fiscal affair theory to reason and prove and is logic starting point to structure fiscal affair theory. Fiscal theory system consists of starting point theory, basic theory, objective theory and operation theory, which is related and interact with each other and propel fiscal affair theory to develop in the direction of practice.