Salicylic acid(SA) at different concentration was tested on conidial germination and mycelial growth of yardlongbean fusarium wilt fungus, disease rate, chitinase and β-1, 3-glucosanase activity of seedling after challenge inoculation in the experiment. The results indicated:that SA at the concentration of above 2.0 mmol/L had inhibition to the conidial germination. At 1.0- 10.0 mmol/L SA had inhibition to the mycelial growth. Without any harm to the seedling, treatment with SA at 0.5 mmol/L was most effective and reduced the infection rate by 63.2 %. SA enhanced the activity of the two enzymes in the susceptible cultivar,compared to the plants without SA treatment. In the plants with prior SA treatment β-1,3-glucosanase and chitinase were activated significantly earlier when the host plants were further challenged by the pathogen.