The relationship between proactivity and employee innovative behavior has always been a hot topic in the field of innovation microscopic research. However, the studies have ignored the mechanism. Based on cognitive - motivation theory, the paper discusses the mechanism of proactive personality and employee innovative behavior . An empirical research is conducted with effective data of 247 employees from pharmaceutical biotech companies of China, exploring the relaionships of employee innovative behavior (EIB), proactive personality (PP), innovative self-efficacy (ISE), innovative outcome-expectation ( IOE). The results show that there are significant correlations between the above variables,and PP indirectly affects employee innovative behavior via multiple mediating of ISE and IOE.