The AS-AD model is one of the main analytic tools in macroeconomics, in majority of textbooks, however, there exist some shortcomings in the expositions of aggregate supply curve such as incomplete or unclear or inaccurate description. In order to make up this deficiency, this paper overall and deeply discusses such three issues as the definition of aggregate supply curve, the meaning of “longterm” and “shortterm” in aggregate supply theory as well as the derivation of main shortrun AS curves. The focus of the discussion is on the key points for correctly understanding of these three issues.