Abstract: Computer viruses play extremely important roles in the anti-virus industry, because their existence makes software developers pay more attention to security and develop anti-virus technology. Therefore, computer viruses and their evolutions are worthy of thoroughly studying in scientific research sense. To further investigate the evolution of computer viruses, an immune genetic algorithm based model for computer viruses evolution is proposed, which draws inspirations from artificial life. The formal definition of computer virus is introduced, and the evolution operators including selection, crossover, inversion, and immune operator are presented. The simulation experiments indicates that computer viruses have enormously potential capability of self-propagation and self-evolution. Some defense strategies are discussed focusing on preventing unknown computer viruses.