The disclosure provides a method for manufacturing an active substance for inducing self-lysis in microalga cells, including: inoculating a bacterial strain belonging to Bacillus into a culturing medium to obtain a bacterial suspension; culturing the bacterial strain belonging to Bacillus at least to a stationary phase to a condition in which the bacterial strain belonging to Bacillus aggregates in the bacterial suspension and the bacterial suspension becomes pellucid; and after the bacterial strain belonging to Bacillus aggregates in the bacterial suspension and the bacterial suspension becomes pellucid, performing a vacuum distillation procedure on the bacterial suspension to obtain an active solution, wherein the active solution contains an active substance for inducing self-lysis in microalga cells.