Image scrambling is an important method to achieve images secrecy. Arnold cat transformation is widely applied, and its scrambling effect is better relatively in the classical scrambling algorithms. But it has some shortcomings of short key qualities and poor universal property. It brings forward an algorithm of image position even scrambling through improving the Arnold cat transformation. On the basis of position scrambling, the image pixel values are scrambled using chaotic map. Experimental results show that the algorithm has many advantages of increasing key qualities obviously, satisfactory effect of scrambling, and the pixel values of the image are both changed.