The testing data of millimeter-wave collision-warning radar were firstly analyzed by time-frequency method. Then a constant false alarm rate (CFAR) scheme for millimeter wave collision-avoidance radar was designed on the basis of the clutter statistics distribution rule. This proposed method can change the threshold with the clutter to make the false alarm rate constant. The testing result and the performance of this CFAR processor were presented. It is shown that this method is practical in the project.