Abstract: After analyzing the basic attribute of freeway，the freeway benefit is divided into economic benefit and social benefit. From microeconomics angle，the function of supply curve and need curve is gained according to the traffic and economy characteristic.Then the freeway supplyneed equilibrium analysis is taken，the producing mechanism of economic benefit and social benefit of freeway is studied. The research will be benefit to objective evaluation of freeway benefit and scientific decision-making of freeway construction items.

Key words: freeway, economic benefit, social benefit, consumer surplus, producers urplus, external effort

摘要： 在分析高速公路基本属性的基础上，从微观经济学的角度，推导了高速公路的供给曲线和需求曲线的函数关系式，进行高速公路的供需均衡分析，研究了高速公路效益的产生机理，为高速公路建设项目的效益评价和决策提供了理论依据.

关键词: 高速公路, 经济效益, 社会效益, 消费者剩余, 生产者剩余, 外部效应