At the end of the 20th century and in the beginning of the 21st century there is an enormous change in global economy. At the same time with competitive economy the industrialized countries emit greenhouse gases which cause global climate change. Day by day the life expectancy increases and economic competitions of the nations change due to open economy. Again the natural calamities such as cyclone, earthquake and tsunami comparatively increase due to global warming, which decrease economic development. So that in the 21st century economy faces with difficult challenges. The net national product, sustainability and social welfare economy, green accounting, optimization in economics, voting system, game theory and health valuation due to environment pollution are parts and parcel of modern economy. The work is prepared considering the economic development emphasizing the above topics.