The invention relates to a composition for treating porcine respiratory tract infection and a preparation method of the composition. The composition is prepared from the following raw materials in percentage by weight: 1-5 % of marbofloxacin, 1-5 % of tiamulin fumarate, 5-15 % of tilmicosin phosphate, 5-15 % of lincomycin hydrochloride, 5-15 % of chlortetracycline hydrochloride, the balance of anhydrous glucose. All the components are grinded, the obtained powder is screened by adopting a No.5 sieve, the screened powder is sufficiently and uniformly mixed, and thus the composition for treating porcine respiratory tract infection is obtained. Compared with the prior art, the composition has the advantages that the plurality of medicines which can be mixed for use are comprehensively selected, the situation that some pathogenic bacteria have drug resistance to some medicines, consequently, treatment failure is caused, is avoided, the drug resistance probability of pathogens is reduced, so that the pathogenic microorganism resisting range is wide, the antibacterial effect is strong, and disease recovery is facilitated.