International direct investment improved the world economic development greatly, and the level of capital transaction of a country indicates its degree of integration into world economy. In China, there exists a serious unbalance between outflow FDI (Foreign Direct Investment) and inflow FDI, and the former is of a extremely small scale. The relationship between outflow FDI and a country's economic development, as well as the relationship between outflow FDI and TFP (Total Factor Productivity) growth rate is analyzed with international comparison and econometrics model. The results show that a obvious positive correlation between outflow FDI and GNP exists, and outfolw FDI of a country improves its GNP growth a lot. Meanwhile, as to the contribution elasticity to TFP, outflwo FDI is much higher than international trade. It is revealed that China not only has necessities, but also has great potentialities to invest in foreign countries. Finally some suggestions are put forward.