A Block Truncation Coding (BTC) method and apparatus thereof are provided, which can avoid the flickers of pixels when applied to moving picture sequence, or increase the quantization levels with a simple and low-cost method. The BTC method includes: (a) receiving an image input of a block containing a plurality of pixels, and calculating the block mean in the pixels X; (b) classifying the pixels into a high intensity group and a low intensity group based on the mean value of the pixels, and assigning a corresponding bit based on which group each of the pixels belongs to, the corresponding bits of all the pixels constituting a bitmap, wherein the pixels or the corresponding bits are stabilized; and (c) calculating the mean value of the pixels of the high intensity group A and the mean value of the pixels of the low intensity group B.