Binarization, possibility model and the entropy engine are the three stages of the arithmetic coding. In order to deal with the new syntax elements in a screen content codec, the binary tree base binarization decision method is proposed in this paper. The syntax probability distribution is derived, and then the bit probability distribution is calculated with the different binarization method. The binary tree method is used to get the optimal bit grouping. Experimental results show that the method proposed in this paper can improve the compression rate by 18.06% in average.