This couse will introduce the core concepts and policy implications of economics. We shall discuss the decision making of choices by consumers, business and government, and three problems: what(choice), how (technology) and for whom (i.e. distribution) to be produced? What is the opportunity costs of one decision-making by economic units? This couse is composed of two parts. Part I covers the topics including demand and supply, international trade, externality and public goods, consumer behavior, market structure, and factor markets etc. Part II consists of macroeconomic topics like the measurement of national income, economic growth, business cycles, money market and financial institutions, aggregate demand and supply, and international finance etc.