The invention discloses a method for converting blue algae mud into an organic fertilizer by thermal composting, which comprises the following steps: concentrating the drained the blue algae mud until the water content is 90-95%, thereby obtaining the concentrated algae mud; adding an environmental induction material, which accounts for 0.1-1.5 wt% of the concentrated algae mud, into the concentrated algae mud; and uniformly stirring, and carrying out thermal composting in a dark place for 3-5 days, thereby obtaining the organic fertilizer. The method disclosed by the invention overcomes the defects of long time, great loss of available nutrients, pathogenic bacteria, viruses, microbial poison accumulation, heavy metal concentration and secondary pollution in the simple composting fermentation, lowers the transportation and storage cost, saves the occupied area and equipment investment, thoroughly implements harmless treatment, and solves the problem in large-scale conversion from wide-resource organic pollutants into the organic fertilizer.