Computer images have permeated many aspects of modern society such as commercs, education and entertainment. Computer animation is typical of artificial image sequences. A great number of image sequence data need to be compressed so as to be transmitted in limited bandwidth or stored in finite capacity memory. Video compression standards are not well suitable for artificial images created by computers. This paper proposes to use structure runlength coding to compress animation sequences. However, extending simply the original structure runlength coding in image sequence may lead to that compression ratios become bad at the case of higher spatial correlation than temporal correlation. This paper suggests to increase a more symbol standing for temporal relation so as to improve the basic structure runlength coding. How to use the new symbol results in three algorithms. Experimental results show that these new algorithms are superior to original structure runlength coding.