An OS-CFAR (Ordered Statistics CFAR) based on a sorting algorithm is useful for automotive radar systems in a multi-target situation. However, while the typical cell-averaging CFAR has low computational complexity, the OS-CFAR has much higher computation effort. In this paper, we design the new OS-CFAR architecture with a low computational effort. In the proposed method, since one time sorting processing is performed for the decision of the CFAR threshold, the whole processing effort can be reduced. When the fast sorting technique is employed, the computing time of the proposed OS-CFAR is always much shorter compared with typical OS-CFAR method regardless of the data size. We also present the processing result of proposed architecture using the real radar data.