The radar target detector is an important part of the radar receiver. The purpose of target detection is to maximize the detection efficiency of the target under the constraint of constant false alarm probability. Aiming at the traditional cell averaging-constant false alarm rate (CA-CFAR) in the vehicle-mounted millimeter-wave radar target detection process tends to be obscured under the condition of adjacent multiple targets, we improves a new one-dimensional CA-CFAR detection algorithm. First, the left and right reference units are divided equally, and the average value of each sub-reference unit after the division is obtained. Then, the average value of the sub-reference unit is compared with the average value of the reference unit. Finally, the average value greater than the reference unit is processed to obtain a new detection threshold. Simulation and experimental results show that the improved CA-CFAR algorithm has better detection performance in linear frequency modulation continuous wave radar multi-target detection compared to traditional CA-CFAR, which demonstrates the effectiveness of the proposed algorithm.