With the developing of the information technology, the information technology plays more important role in economy. The information technology innovation's forming process not only produces economic effect itself, but also has some influence on the other related industry. The influence effect analyses of the information technology on the economic growth includes two parts : The information technology innovation's forming and spreading. The former mainly is the information technology itself on economics influence effect; The later mainly is that the non information technology industry economic effect caused by the information technology innovation. This paper's emphases research that how much is the information technology innovation and spreading effect during different period in order to make sure what period produce Spillover Effect and what period produce Substitution Effect. The Spillover Effect technology can bring the benefit to the third party and Substitution Effect cannot. The problem will direct influence the state policy . It also used to reflect and measure how a kind of technology advancement influencing to economic growth. Here first we'll do some theory analyses to the effects of the information technology innovation's forming and spreading, i.e to find out their effect rules. And then we'll do some demonstration by using the real example and further analyses the influence effect of the information technology on the economic growth with the mathematics, and find out the conclusion: In the lower informationization period, The information technology is a Spillover Effect technology. During the higher informationization period, the information technology is a Substitution Effect technology. The conclusion will be redound to the harmony develop for the IT industry and the economic growth. Finally offer a series of the suggestions about information technology.