The invention provides a basic nutrient solution, and a preparation method and application thereof and belongs to the technical field of microbial agents. By using the invention, an autotrophic nitrifying bacteria liquid which is high in activity and can be rapidly and uninterruptedly increased in an aeration tank can be obtained. For the basic nutrient solution provided by the invention, the concentration of Na2CO3 is 2 g/L-5 g/L, the concentration of K<+> is 0.1 g/L-0.5 g/L, the concentration of Mg<2+> is 0.01 g/L-0.2 g/L, the concentration of H3PO4 is 1.5 g/L-2.8 g/L, the concentration of growth factors is 0.1 [mu]g/L-50 [mu]g/L, and the concentration of trace elements is 0.1 mg/L-5 mg/L. The preparation method of the basic nutrient solution provided by the present invention comprises the following steps: weighing the component based on weight and adding tap water for dissolving so as to obtain the basic nutrient solution.