The invention provides a preparation method of a biochar-based material, the biochar-based material and application of the biochar-based material, and belongs to the technical field of organic substance degradation. The preparation method comprises the steps that an inorganic salt liquid culture medium and biochar are mixed to obtain a mixture, phenol-degrading bacteria are inoculated in the mixture for culture for 45-50 h, and an obtained culture material is subjected to vacuum suction filtration to obtain the biochar adsorbing the phenol-degrading bacteria; after the biochar adsorbing the phenol-degrading bacteria is resuspended with normal saline, a suspension liquid is obtained, and the suspension liquid and a sodium alginate solution are mixed and then dropwise added into a calcium chloride solution to obtain the biochar-based material. By adopting the biochar-based material prepared with the preparation method, the degradation rate of phenol is greatly increased, for wastewater contaminated by phenol with the concentration of 600-1,200 mg.L<-1>, the biochar can significantly improve the tolerance of the phenol-degrading bacteria to the toxicity of the phenol, and the final degradation rate of the phenol is close to 100% at most.