An accelerator driven sub-critical system (ADS) that utilizes spallation neutrons as an external neutron source to drive the sub-critical blanket system has inherent safety features. It is universally regarded as the most promising approach for the disposal of the long-lived nuclear wastes because of its hard and wide neutron spectra, and large flux. In addition to its ability to reduce significantly the lifetime and volume of nuclear waste, it also has the potential for nuclear fuel breeding and nuclear power generation, which could improve the utilization efficiency of nuclear fuel resource. In this paper we describe the basis principles, challenges and current status of ADS research worldwide. A brief review of the progress of China's ADS research program is then presented, followed by an overview of the outlook for future developments.