Among the domestic population of using network today, the using rate of the Instant Messaging (IM) has been greater than 80% already. With organizations’ gradual exoteric Instant Messaging usage in the workplace, Instant Messaging has already caused unprecedented influence on employees’ communication. In the past, researches of IM just only focused on users like students or teenagers, there were rare researches on business employees. The research method in this paper is survey and 303 respondents are received. This study is adopting Partial Least Squares（PLS） to analysis the collected data. The result of statistical analysis provide several conclusions as following (1)social influence positive influences IM behavior; (2) perceived IM capacity positive influences IM behavior; (3) computer self-efficacy negative influences IM behavior; (4) task nonroiutineness positive influences IM behavior; (5) IM behavior positive influences organizational formal communication satisfaction; (6) IM behavior positive influences organizational informal communication satisfaction.