The process of target detection of FMCW mmWave vehicle mounted radar can be easily affected by clutter. To address this issue, a detection method that can effectively suppress clutter is proposed. Firstly, the companding algorithm is used to improve the three-frame difference method. In this way, it can better separate the clutter and target signal in the echo waves. Then, the CFAR algorithm is introduced to filter the clutter in the echoes, and the density peak clustering algorithm is used to find the target clusters. Finally, the power value of the target point in the target cluster is converted into the corresponding weight to improve the classical center of gravity method. The accuracy of target positioning is effectively improved. Experimental results show that the detection accuracy of this method reaches 96. 5% , 95. 9% , 95. 6% , and 94. 4% in four scenarios, including parking lot, straight road, urban street and campus road. Meanwhile, in terms of detection speed, the processing cycle of single frame radar echo signal can reach about 0. 3 s, which can meet the requirements of practical applications.