As mentioned above article, theoretical base of the international trade were distinguished under three categories such as classical, neoclassical and modern theories. Classical views of international trade were emphasized on three main factors. It includes gains from the trade, Structure and Direction of trade and the terms of trade. Likewise, neoclassical thoughts were also based on three factors such as Introducing social indifference curve, Introduce offer curve and Edgeworth and Concept to determine equilibrium of the international trade. Unlike the concept of constant opportunity cost in classical thoughts, neoclassical views are mainly based on increasing opportunity cost.