A circuit for detecting motion pictures includes a first-stage motion picture detecting unit and a second-stage motion picture detecting unit. The first-stage motion picture detecting unit analyzes a current image frame and a previous image frame to calculate a first motion value associated with the current image frame. The second-stage motion picture detecting unit receives the first motion value, compares the first motion value against an adjusted motion value, and outputs and stores a larger one as a second motion value. The adjusted motion value is a value derived by adjusting an adjacent previous second motion value.