The invention discloses an actinobacillus pleuropneumoniae serotype 2 bacterial strain and its preparation method, which is actinobacillus pleuropneumoniae serotype 2XT, wherein the CCTCC NO. is M2011410. The preparation method comprises the following steps: 1) medium preparation, A) weighting yeast powder, glucose, monosodium glutamate, MgSO4, FeSO4.7H2O, dissolving into pure water, regulating pH value and disinfecting; B) weighting NaH2PO4 and K2HPO4 to prepare mother liquor and disinfecting; C) weighting NAD to prepare mother liquor, filtering by a filter membrane; D) mixing the solutions obtained in the step A, the step B and the step C according to amount to obtain the medium; 2) fermentation and culture, a) activating the freeze-drying seeds by NAD-contained TSA plates until single colony is grown out; b) selecting single colony and culturing by shaking a bottle; c) transferring cultured seed liquid to the fermentation medium; d) low stirring at initial fermentation period, and low ventilating; e) raising rotating speed at logarithmic phase and ventilating, and on-line controlling pH value; f) improving dissolved oxygen, and placing into a tank and collecting bacterium. The actinobacillus pleuropneumoniae serotype 2 bacterial strain suitable for preparing inactivated vaccine has the advantages of strong toxicity, good antigen effect, low price, fast mycelium growth, highdensity and easy control.