The invention discloses an acidic soil secondary-obstacle repairing agent as well as a preparation method and application thereof. The acidic soil secondary-obstacle repairing agent comprises the following raw materials in parts by weight: 30-80 parts of biomass ash, 5-30 parts of phosphate rock, 3-30 parts of tobacco stems and 3-30 parts of bone meal. According to the invention, an acidic soil conditioner is developed based on the biomass ash, phosphate rock, tobacco stems, bone meal and the like, to increase a pH value of the acidic soil while providing rich trace elements for soil and inhibiting generation of pests and diseases. The invention solves biomass ash stacking, difficult storage, dust emission, high pH value and other environmental pollution problems generated in biomass power plants, and realizes comprehensive utilization of the biomass ash, tobacco wastes, bone meal and other waste resources.