4D-CT scanner is a high-speed cone-beam CT with good low- contrast detectability. In a single rotation, a voxel data set with higher spatial resolution over a wide z-axis can be obtained. Using continuous rotation, temporarily continuous voxel data sets and 3D dynamic images can be acquired. We have developed a 4D-CT prototype system using a large area 2D detector with high speed rotating gantry. The key technologies for 4D-CT scanner are a large area 2D detector, high-speed and continuous rotating gantry with high-speed data transfer. The full size 2D detector for prototype system has 912 channels, 256 detector rows for 0.5 mm slice thickness, and the sampling speed is 900 view/s. The rotation speed of the gantry is 1.0 s/rotation, and the speed of the data transfer system must be more than 5Gbps. The data transfer system consists of laser diode and photo diode. We have got real-time volume images of crayfish, moving jaw and breathing lung. We will start clinical research at next stage, and continue to improve the image quality.