Spirulina platensis has roles in biotechnological product advancement due to its safety for humans and animals. Analysis of S. platensis extract by high-performance liquid chromatography reflected the presence of 14 phenolic and flavonoid compounds with different concentrations such as ellagic acid (333 µg/g), gallic acid (294 µg/g), methyl gallate (147 µg/g), naringenin (144 µg/g), and chlorogenic acid (142 µg/g). The isolated Aspergillus flavus from silage of maize was tested to evaluate the effect of S. platensis extract on aflatoxins B1, B2, G1, and G2 production. The treated silage with S. platensis extract showed the presence of 37±0.33 ppb, 0.59±0.16 ppb, 0.26±0.22 ppb, and 0.21±0.18 ppb compared to un-treated silage that showed 3.14±0.15 ppb, 0.81±0.08 ppb, 0.46±0.05 ppb, and 0.26±0.23 ppb aflatoxins of B1, B2, G1, and G2. These results were shown on the 10th day of incubation. On the 15th day of incubation, the treated silage showed less mycotoxins than un-treated silage. At different incubation periods, glucosamine was estimated as a growth development biomarker. The content of glucosamine was inhibited as a result of the effect of S. platensis extract on fungus growth with 53.71%, 49.19%, 47.84%, 38.47%, and 35.72% inhibition on the 3rd, 6th, 9th, 12th, and 15th day.