Frame duplication forgery is a very common operation for video tampering in the temporal domain.By removing some frames which contain a crime scene or crime evidence,the forger can change the video content.A lot of solutions have been proposed for detecting this type of tempering operation.However,there are two disadvantages.The first one is fixed threshold;the other is huge computation.In general,frame duplication forgery and re-compression would be performed on a video at the same time.Since re-compression will cause data lost,the fixed thresholds may lose their effects.Therefore,an algorithm based on dynamic threshold is proposed in this paper,which can improve the robustness.Additionally,the proposed method adopts dictionary order algorithm to reduce the search scope of frame matching and the time complexity.Three performance indices:precision,recall and average computation time per frame are employed to evaluate our algorithm.The results demonstrate that the proposed method outperforms the existing methods in terms of precision,recall and computation time.