This paper analyses the trends of GDP and Green GDP for forecasting sustainable development of South Asian countries. It highlights the environmental sustainability, Green GDP accounting methods and impact of Green GDP on GDP. It also up holds limitations of traditional GDP, future of Green GDP and prepares theoretical framework for Green GDP. To analyze the relationship and to calculate the gap between GDP and Green GDP a developed econometrics model of panel data was used on eight South Asian countries. The researchers used IPS test for checking panel unit root and found variables are stationary. The result of Pedroni test for cointegration shows that there is a long run cointegration between GDP and Green GDP in different nations of South Asia. The results also imply that South Asian countries could increase GDP by reducing environmental damages which will promote sustainable development. Sustainable development can only be achieved through the integration of policies that connect environment, economy and society on a parallel line.