Abstract: In this research, Beauveria bassiana Bals mass release efficiency for microbial control of Saw-toothed beetle, Oryzaephilus surinamensis L. was studied in Date palm stored condition. For this propose, effects of treatments including B. bassiana fungus spore and methyl bromide fumigation on the Saw-toothed beetle population reduction was studied during the 25 weeks of storage period. Results showed that, population fluctuation of saw-toothed beetle in microbial control (χ2 = 9752.72) and methyl bromide fumigation (χ2 = 2281.47) treatments had significant difference. Freedman and Kendal concordance test also showed significant difference between microbial control and Methyl Bromide fumigation. The microbial control treatment acted in population density dependent manner and caused pest population reduction so that the control efficiency always was near to 60% and the highest level of it was 80% that occurred on the 3rd month of storage period. Maximum efficiency of methyl bromide treatment was about 90%. The efficiency of this treatment was reduced from the second month onwards so that the repetition of control operation was necessary.