The present invention discloses a method for preserving a probiotic composition, including: providing a bacterial cell suspension, which is one or more bacterial cell suspensions of a bacterium or Saccharomyces boulardii; mixing the bacterial cell suspension with a sodium alginate solution or an alginic acid solution; and adding the mixture to a calcium ion solution until the mixture is immobilized in a shape. The technology of the present invention has the effects of long-term preservation at room temperature and resistance to high temperature, and can be applied to ordinary bacterial strains, without being limited to a small number of bacterial species able to form endospore, and without requiring the strains to be frozen for preservation. The method of the present invention can be applied to the preparation of aquatic feeds, animal feeds, or probiotics that human beings need.