The invention relates to a method for preparing a seaweed organic-inorganic fertilizer containing glycotropic bacillus strain. Dried seaweed is ground into powder, the seaweed powder is added to water according to a certain proportion, and the mixture is placed in a fermentation tank and then sterilized at a certain temperature for a certain period of time; a seed solution is prepared; a fermentation strain YIC-ALG3 glycotropic bacillus capable of degrading alginic acid is obtained through screening, and a liquid culture medium is then inoculated with the fermentation strain for culture lasting a certain period of time; the seed solution is added into the fermentation tank according to a certain mass ratio to be fermented under a certain condition, the fermentation condition is adjusted after fermentation, the fermentation condition is adjusted again and the seed solution is supplemented after a certain period time of storage, glycotropic bacillus is obtained after three times of adjustment, and glycotropic bacillus is added to organic-inorganic fertilizer in an external wrapping mode to obtain the seaweed organic-inorganic fertilizer containing glycotropic bacillus strain. The fermentation process is stable and controllable, fermentation period is short, product functions are remarkable, and the fertilizer is suitable for large-scale production.