The user interface tends to migrate from “technique centered” to the new stage of “user centered”. As a main interface that fits this trend, two-handed inte raction is becoming more and more important due to its naturalness and intuitive ness. The state of the art of the two-handed user interface is presented systemi cally. Based on the research of the behavior and psychology of bimanual operatio n, several interface design principles are concluded from the experimental evalu ation. Further more, the classification and comparison of several typical two-ha nded interaction techniques are discussed. Finally, some unresolved problems are analyzed and the future research directions are given.