The present invention relates to the multimedia communication technology, in particular to the technology of real-timely detecting advertisements in broadcast data flow. The present invention discloses a method and a device for real-timely detecting advertisements in broadcast data flow in order to reduce the requirements on the configuration of the storage capability of a system when advertisements are real-timely detected. By the combination of silence detection and shot transition detection, the present invention utilizes the structural characteristics of advertisements and the characteristics of the spots of a television station to real-timely detect advertisements. The present invention also discloses a device used for real-timely detecting advertisements in broadcast data flow; after receiving the broadcast data flow, the device detects and judges the broadcast data flow and real-timely detects an advertisement sequence which is then processed.