Unfavorable oral bioavailability is an important reason accounting for the failure of the drug candidates. Considering the lack of in vitro high-throughput screening assay for oral bioavailability, it is critical to develop in silico models for early predictions of oral bioavailability. In this review, we summarize present knowledge and recent progress related to the in silico prediction of oral bioavailability, including the current available datasets of oral bioavailability in human, the roles of physiochemical properties contributing to oral bioavailability, and the available theoretical models to predict oral bioavailability. Particularly, the regression model recently developed by us was demonstrated, which is based on the largest dataset of oral bioavailability in human. Although promising progress has been made recently, it is still indispensable to improve the accuracy of the models to predict oral bioavailability.