Aiming at the issue of safety of intended functionality (SOTIF) of adaptive cruise control (ACC) system caused by the large unintended measurement error of target movement of millimeter wave radar in heavy rainfall scenes, a SOTIF safety control strategy for ACC system in heavy rainfall scenes is proposed in this paper. Firstly, double-state Chi-square is used to check the target information output by millimeter-wave radar to determine whether there exist SOTIF risks. Then the target information with safety risk is corrected by Kalman filter, with the target information corrected input into ACC controller to control vehicle motion state for achieving safety control. Finally, the Prescan/Simulink co-simulation platform is built to conduct verification simulation on the safety control strategy proposed. The results show that double-state Chi-square test can timely detect risk information with a detection time deviation within 1.31 s and a distance correction error of Kalman filter within 3.66 m, effectively ensuring the safe and stable operation of ACC system in heavy rainfall scenes.