In recent years there is a considerable trend to use bioactive compounds in food formulation. Acorn represent good resource of nutritional compound and biologically active compounds such as tocopherols and phenolic compounds. The aim of this study was to evaluate the effect of ethanolic and aqueous extract of acorn on microbial and sensory properties of prebiotic and egg-free salad dressing during 30 days of storage at 4 °C. Extraction of ethanolic and aqueous extracts from acorn was carried out in soxhlet extractor. These extracts were added to sauce samples at concentrations 1 and 0.5%. pH, acidity, microbial count of acid tolerant bacteria, mold and yeast were measured and sensory evaluation was performed on days 3 and 30 after production. The results showed that the use of extracts in salad dressing improved microbial quality in the final products.Growth of microorganisms decreased significantly with the increase in the concentration of aqueous and ethanolic extracts. The results of pH evaluation of sauce samples indicate that pH changes in samples containing acorn extracts were significantly lower than other samples. Also, increasing the concentration of acorn extracts was led to drecrease of acidity changes in sauce samples. However, increasing the storage time significantly increased the titratable acidity of all samples. so that the salad dressing containing 1% ethanolic extract had the highest overall acceptance compared to other samples. Results indicated that the use of acorn extract and inulin in the formulation of salad dressing can improve the chemical, microbial and sensory properties of salad dressing.