The study on metabolism and biotransformation of natural products by human intestinal bacteria is receiving more and more attention. To gain insight and to trigger additional research in this field, we provide in this an overview of selected natural products bio-transformed or metabolized by human intestinal bacteria through the reported literatures in recent 20 years. The mechanism as well as pathway of metabolism or bio-transformation by human intestinal bacteria was discussed, according to the categories of natural products such as flavonoids, terpenoids, phenylpropanoids, alkaloids, steroids and the others. We also address the needs in further studies on metabolism and conversion action of natural products by human intestinal bacteria.