A method, apparatus, electronic device, and a system for selecting a to-be-masked region in a video are disclosed. The method includes: obtaining a video to be detected; determining specified target sets in the video through a preset target detection algorithm, wherein each specified target set is a set of pixels of one specified target in video frames of the video; determining whether a specified target corresponding to each specified target set is a sensitive target respectively through a preset recognition algorithm; and using a specified target set as to-be-masked regions in the video when a specified target corresponding to this specified target set is determined as a sensitive target. In this method, specified targets are first determined, and then it is determined whether the specified targets are sensitive targets.