General difference expansion algorithms embeds watermark by expanding difference between pixel pairs,and the maximum embedding rate is 0.5bpp.The disadvantages of these algorithms are low embedding rate and large distortion.In order to achieve higher embedding rate and better invisibility, a novel reversible waterm arking algorithm is proposed based on the differences expansion of pixel ternaries.The cover image is firstly divided into pixel tern aries,by utilizing the correlation of image pixels;the local variance of the pixel ternary mean is used to select the smooth region. Se condly,expand the differences between pixels and the mean of the pixel ternaries separately,and then embed one bit of secret data to the each expanded difference.The threshold is set to limit the change of pixel value when embedding watermark in the smooth region so as to improve the imperceptibility of the images and prevent pixel value overflow or under flow occurs.The maximum embedding rat e of the proposed algorithm reaches 0.66bpp, which is 33% higher than the conventional differential expansion algorithm.The experimental results show that the proposed algorithm can maintain a higher peak signal-to-noise ratio at a high embedding rate,effectively improve the watermark embedding capacity,and reducethe distortion rateof the image.