Bacillus sp. Za, a biodegradable strain with diphenyl ether herbicide, was used as the material to prepare microbial preparation. The material ratio of liquid protective agent was optimized, and the most suitable material for solid preparation was screened. The results showed that: 1) The protective agent of liquid preparation (0.20% sodium citrate, 0.20% carboxymethyl cellulose, 0.30% KCl) increased the number of viable bacteria by 35.71%, and the degradation rate of 50 mg/L lactofen in liquid preparation stored for 30 days was 83.50%. 2) The optimum material for solid preparation of pig manure organic fertilizer was obtained. After 60 days of storage, the viable bacteria count of solid preparation was 8.26×10⁸ cfu/g, and the degradation rate of 10 mg/kg lactofen in soil was 85.52%. 3) Adding solid preparation can effectively alleviate the drug damage caused by the residue of lactofen on maize.