Bioethanol is one of the most employed liquid biofuels due to the easy adaptability of this fuel to existing engines and because this is a cleaner fuel with a higher-octane rating than gasoline. Among the widely used substrates for ethanol production is sugarcane molasses. Unsuitable storage of molasses results in deterioration of fermentable sugars, consequently ethanol yield quality and efficiency. The present study aimed to shed light on the effect of the storage period on the efficiency of sugarcane molasses and its effect on ethanol fermentation efficiency in distillery factories. The results showed that the total fermentable and non-fermentable sugars involved in sugar cane molasses varied between samples that were collected according to the location source. Also, ethanol yield and fermentation efficiency were different in the fermented molasses media, which contained the same concentration of fermentable sugars. About 2.65 - 11.20% of fermentable sugars in molasses were lost when stored under different temperatures. The loss was increased with the increasing storage temperature. Most of the loss happened in the first two months, especially at high temperatures. The decrease in ethanol yield and fermentation efficiency was affected sharply in the molasses storage at high temperatures than the low ones. From this study, the suitable storage temperature must not exceed 40°С to maintain molasses quality and avoid molasses deterioration by heat in temperatures.