Abstract: Based on the concept of knowledge stock,firms are devided into innovation leaders and innovation followers, and then we modifies the technological-push, demand-pull model of firm R&D developed by Lee(2009) to find the differences between the R&D investment decisions of the two kinds of firms in different stages of their industry lives.Using the data of the pharmaceutical firms and the computer and office equipment manufacturing firms which are listed on Shanghai and Shenzhen Stock Exchange from 2012-2015,the differences are proven.The result shows that compared to the innovation followers,the innovation leaders in the growth stage of the industry life cycle are more likely to exhibit a higher level of R&D investment when facing the intensifying competitive market pressure .During the mature stage of the industry life cycle,innovation followers prefer to improve the level of R&D investment when facing the intensifying competitive market pressure and the innovation leaders do not.