Abstract: An environmentally responsive Paecilomyces lilacinus microbead and its preparation method and application are provided. The Paecilomyces lilacinus microbead includes a capsule core and a capsule wall; wherein, in the capsule core, Paecilomyces lilacinus spore powder, a vegetable oil, glucose, peptone, a cellulose nanofiber, sodium citrate, and a surfactant are combined to form an emulsifiable capsule core; and in the capsule wall, chitosan, gelatin, polyvinyl alcohol, glycerol, and water are combined to form a water-responsive shell. The environmentally responsive Paecilomyces lilacinus microbeads can stimulate the dissolution of polyvinyl alcohol in the shell according to the moisture content in the soil, so that the water in the soil flows into the microbeads. The cellulose nanofibers in the microbeads absorb water and expand, blocking the holes in the shell, resulting in the inability of spores to flow out.