A real-time moving object extraction and tracing algorithm is proposed for videophone application. Semantic objects, mainly moving objects in this specified case, are extracted by block based change detection from first several frames. Improved active contour model is then utilized for object tracing. Since there is little difference between continuous two frames, only limited pixels need to be searched instead of whole frame scan so that computing complexity is greatly decreased. Therefore, it is able to be used for real-time applications such as that in videophone. However, previous active contour model is sensitive to noise. Error originating from noise traps accumulates and deteriorates the tracing results. So gradient projection (GP) and jump back (JB) mechanisms are introduced to suppress noise trap effect and error accumulation in this paper. Experiment results demonstrate that proposed algorithm is an efficient noise tolerable real-time approach.