This paper proposes a rapid image matting method based on categorized video sequences. The image sequences in a video are classified into three categories:key frames, trivial-changed frames and variant-changed frames. Different image matting algorithms are adopted to treat each image sequences category. First, the method uses closed-from image matting algorithm to process the key frames and get the alphas, foreground colors and background colors. Then, the proposed method uses the known values of key frames to estimate and optimize the alphas of the trivial-frames based on frame-coherence. After that, the matting algorithm is processed by utilizing a SIFT Flow based information propagation strategy to transfer informs from key frames to variant-changed frames. The proposed method achieves acceptable matting results and more higher efficiency compares to traditional methods.