This paper analyzes the effect of import taxes and differentiation on the licensing modes choice and social welfare with a differentiated duopoly model in the Stackelberg competition. It shows that fixed-fee can occur if import taxes are high and the goods are very different. Royalty and two-part tariff can increase the profit of foreign enterprise and two-part tariff gain the highest profit. However, three licensing modes may decrease the social welfare under the condition of high import taxes and differentiated goods.