Abstract: A phage composition and an use thereof in strengthening soil carbon fixation, said phage composition including three phages, namely, a polyvalent phage ?YSZKP that attacks Klebsiella pneumoniae and Pseudomonas aeruginosa; a Bacillus cereus phage ?YSZBA1; and a Bacillus cereus phage ?YSZBA2. In the present invention, the phage composition is injected into the target soil, and an approach of strengthening soil carbon fixation by means of cooperation with the host bacteria through injection of AMGs from the phage is employed; at the same time, the phage has a function of regulating the soil microbial communities from bottom to top; a network of symbiosis with indigenous bacteria is further optimized, and the soil carbon fixation potential is improved. This technique is an environmental improvement technique that achieves a good carbon fixation effect, has a low price and is environment-friendly.