The invention relates to a video aided analytical method for criminal investigation and case detection and a system; the system comprises a case file management device, a video library management device, a video decoding and playing device, a blur video processing device, a video analysis and target feature extraction device, a video indexing device and a string case combination analysis device; the method comprises the following steps: case files are built; the related video in the case is imported in a computer system, and the videos related with the case are associated with the case by a relational database; the videos related with the case is analyzed intelligently, feature information of an interested target is extracted from the video and is stored; a user inputs indexing conditionson a system interface, so as to comprehensively and intelligently index the videos and search the video clips. The system has the functions of intelligent indexing to the videos, quality improvement and string case-combination analysis, realizes unified management of the case videos and the comprehensive analysis platform, improves the video inspection speed, and enhances the effect and accuracy of fighting against crimes.