The invention discloses a Rhodococcus strain ZWL3NT CCTCC NO: M 208206. The preparation method of the strain includes formulation of an inorganic salt substrate, strain concentration, separation and degradation of bacteria, wherein the inorganic salt substrate contains Na2HPO4.12H2O, KH2PO4, MnSO4.H2O, FeSO4.7H2O and other components; the bacterial concentration includes: formulating the soil sample and inorganic salt substrate into a suspending liquid, inoculating the suspending liquid in a certain volume of inoculating amount onto a fresh inorganic salt medium containing 3-nitrotoluene, shaking table culturing at constant temperature until obtaining the accumulation culture object with significant degradation performance; the separation adopts a plating technique to separate and purify the culture in the LB medium. The bacterial strain provided by the invention can be used to degrade the 3-nitrotoluene with the degradation rate of 99 percent, and the preparation method is simple and easy to operate.