The invention relates to a method for treating sewage and reducing sludge generation through compound microorganism bacterium agent. The method includes the steps that innovative special strain species and the efficient compound microorganism bacterium agent prepared in proportion are added in the sewage treating process, compositions and functions of original microorganisms in sewage are intensified, it is promoted that organic contaminants and dead biological bacteria are continuously decomposed, and the generation amount of sludge is thus decreased. The technology problems that in sewage treatment plants in the prior art, the generation amount of sludge is extremely large, the sewage treatment range and capacity are insufficient, and the after-treatment cost is over high are mainly solved.