Status of economic development in Shaanxi Province is analyzed, showing that Shaanxi Province has achieved the fast and stable economic growth; and total GDP and fixed assets investment have shown a sustainable growth. According to the time series statistics of Shaanxi Province in the years 1978-2008, Cobb-Douglas Function is used to carry out the empirical analysis on the contribution of fixed assets investment and labor input to economic growth of Shaanxi Province, China. Result shows that capital and labor input are the major driving forces for the economic growth of Shaanxi Province. In other words, economic growth mode of Shaanxi Province is still extensive. Economic growth of Shaanxi Province is increasingly dependent on capital investment and technological progress. Contribution rates of capital and labor to economic growth are 66.9% and 33.1%, respectively. Therefore, investment is a source of economic growth in Shaanxi Province through the reform and opening up in the last three decades.