1. A video stabilization system, comprising: a block motion estimation unit for detecting a plurality of feature points of an inputted image frame and performing a block motion estimation to the inputted image frame by using the feature points as reference points, thereby generating a plurality of block motion vectors corresponding to the feature points; a global motion estimation unit which is electrically coupled to the block motion estimation unit for performing a histogram statistic onto the block motion vectors so as to determine an initial static background motion vector, and for correcting the initial static background motion vector by adopting a Gaussian distribution model and a Maximum a Posteriori (MAP) estimation to generate a global motion vector; and a smoothing unit which is electrically coupled to the global motion estimation unit for performing a smoothing process onto the global motion vector to generate a smoothed global motion vector.