As most emerging markets,China,India,Russia and Brazil are going through a rapid demographic transition.In the mid phase of the demographic transition,each country will experience the Demographic Windowof Opportunity,which might have a positive effect on its economic development.However,during the final phase of the demographic transition,a dramatic aging wave will arrive and exert its negative influence on economic and social development.The BRICS have achieved great economic growth in the last decades.As we try to focus on the bright prospect of the demographic transition,we also have to keep in mind the potential risks residing in the global aging wave inevitably brought by the transition.Brazil,Russia,India and China are at different pace and stage of the demographic transition.In analyzing the demographic transitions of the four countries,the research draws experience from those that have successfully taken advantage of the Demographic W indowto attain fast economic development;the research also attempts to observe the trends displayed by each country’s aging population,and thereby to identify the obstacles each country within its distinct economic framework might have to face in the future. As most emerging markets, China, India, Russia and Brazil are going through a rapid demographic transition. The mid phase of the demographic transition. Each country will experience the Demographic Window of Opportunity, which might have a positive effect on its economic development. , during the final phase of the demographic transition, a dramatic aging wave will arrive and exert its negative influence on economic and social development. BRICS have achieved great economic growth in the last decades. As we try to focus on the bright prospect of the demographic transition, we also have keep in mind the potential risks residing in the global aging wave inevitably brought by the transition. Brazil, Russia, India and China are at different pace and stage of the demographic transition. In analyzing the demographic transitions of the four countries, the research draws experience from those that have have taken advantage advantage of the Demographic W indowto attain fast economic development; th e research also attempts to observe the trends displayed by each country’s aging population, and thereby to identify the obstacles each country within its distinct economic framework might have to face in the future.