A method of in-situ remediation of arsenic-contaminated soil, the method including: 1) inoculating a bacterial strain including Pseudomonas putida MnB1 in a culture medium where the addition amount of the bacterial strain accounts for 2-10% (v/v) of the culture medium; shaking the culture medium including the bacterial strain at the rotation speed of 100-180 rpm at 15-35° C. for 1-5 days under the aerobic condition thereby yielding an enriched bacterial strain; and 2) adding the enriched bacterial strain, manganese carbonate, ammonium ferrous sulfate, sodium citrate, and yeast extract to an arsenic contaminated soil; adding water to the soil until the soil has a moisture content of 50-70%, stirring the soil for 5-30 min, and culturing the bacterial strain in the soil under the aerobic/microaerobic condition at 10-40° C. for 2-6 weeks.