The open access movement of scholarly journals which argues the articles should be freely accessible online without cost to readers because public-funded journal is “public good” rather than “private good”. However, if this argument is reasonable, what the theoretical perspective does it base on? Although many researchers focus on open access issue, many of them put much more analysis on empirical data. This article will examine the open access issue from the theoretical level, adopting the theory of “knowledge commons” and observing the new phenomenon through this theory. The article is separated into three parts: firstly, it will introduce the open access movement; secondly, from theoretical debate, it will introduce the theory of knowledge commons that can help us discover more interesting phenomena which we ignored before; finally, the significance of social sharing is the critical issue when we talk about the open access.