In order to overcome the slow speed of image encryption for android phone, an image block encryption algorithm based on pixel xor is proposed for the Android Phones. In this algorithm, the classic RC4 algorithm in cryptography is modified, and then applied to this paper’s encryption algorithm. Firstly, the original image is divided into blocks. Then, the improved RC4 algorithm is applied to the operation between the adjacent two subblocks, thereby changes the value of pixels. Finally, the image is scrambled by logistic map. Experimental results show that the image has a noiselike characteristic and a flat histogram after the original image is encrypted, and that the algorithm has an enough large key space, a very high sensitivity to the key and a fast speed of image encryption for android phone and the encrypted image has a good randomness and has a low correlation between two adjacent pixels.