To establish virtual avatar systems at the computing environments with limited resources, we design such a system based on single image which can generate speech animation with different facial expressions. Firstly, facial feature points are extracted automatically or manually based on MPEG-4 facial animation to build the face model. Then, according to Facial Animation Parameters of visual phoneme and expression stream, the feature points after image warping are calculated. The next step is to generate the in-between frames by using the image warping algorithm based on scan lines and combining with the correlative time parameters. Finally, with adding the actions such as nodding, shaking heads and winking, the face animation is implemented. Experimental results show that the proposed system can generate smooth and realtime facial expressions under platforms with low computing capacity.