The invention discloses a method for treating antimonous wastewater with modified blue-green algae. The method includes: at room temperature, adding modified blue-green algae adsorbent into antimonous industrial wastewater according to a solid-liquid ratio and a g/ml ratio being 1:50, performing rotational oscillation for 1h, performing centrifugal filtration, measuring concentration of trivalent antimony in residual supernate wastewater, and discharging the wastewater qualified by detecting; settling and filtering saturated blue-green algae adsorbent, adding desorbent to allow desorption for 1h, performing centrifugal filtration, washing with ultrapure water until neutrality, freeze-drying at -50 DEG C to finish regeneration, and using the regenerated modified blue-green algae to carry out an absorption and desorption process under same conditions for five rounds. The method has the advantages that raw materials are easy to acquire, the cost is low, a preparation process of the blue-green algae adsorbent is simple, low in cost and low in time and labor consumption, and in addition, the method features high absorption rate, high absorbing capacity, high selectivity, process simplicity and operational convenience.