Abstract: The influence of ultrasound-assisted calcium chloride marination treatment was studied to accelerate calcium ion penetration and improve beef tenderization effect. A response model was established by the Box-Behnken response surface method. The paper analyzed the effects of ultrasound intensity, calcium chloride concentration, ultrasound treatment time, and their interactions on beef tenderness. The muscle fiber gap and diameter in paraffin-dyed sections were measured to compare tenderization effects. The results showed that the response model was valid in analyzing and predicting tenderization effect. Beef tenderness was significantly improved by ultrasound intensity(p＜0.01), calcium chloride concentration(p＜0.01), ultrasound treatment time(p＜0.01), the interaction between ultrasound intensity and calcium chloride concentration(p＜0.01), and the interaction between ultrasound intensity and ultrasound treatment time (p＜0.05). The optimum conditions of ultrasound-assisted calcium chloride marination treatment on beef tenderness were ultrasound intensity ranging from 200～220 W/m2, calcium chloride concentration 0.25～0.30 g/L and ultrasound treatment time within 10～15 min. Under the above-mentioned conditions, the shear force of Qinchuan bull longissimus dorsi ranged from 36.65～39.89 N, the diameter of muscle fiber significantly decreased, and the gap of muscle fiber largely increased, consequently, the beef tenderization effect was satisfactory.