When previous scholars analyzed regional or national economic growth rate and their sources, they usually used Solow Growth Calculation Model to obtain mean value by making brief sum of economic growth rate and its sources of all regions but overlooked its proportion of each region to all regions or the whole country. Based on the related income function theory, when regional or national economic growth rate and its sources are analyzed, economic growth rate and its sources of each region should be calculated by weight and Solow Growth Calculation Model should be improved on the level of decision unit, subset and sylloge to get the proportion of regional total output to the output of all regions or the whole country on theoretical basis and by method of weight. According to the improved Solow Growth Calculation Model, this paper makes empirical analysis of China’s economic growth rate and its sources since 2000, the results show that GDP growth rate is higher from the calculation by improved Model than by original Model and that labor contribution rate and TFP contribution rate are significantly underestimated for west regions of China but capital contribution rate is highly estimated by unimproved Model.