Information technology (IT) and open innovation has been one of hot topic in existing research respectively. However, there are lack empirical research on inner mechanism of internal IT capability affecting open innovation performance. According to dynamic capability theory, this paper puts internal IT capability, internal knowledge integration, firm social capital, and open innovation performance into a theoretical model. Through 232 surveys, the results indicate that internal knowledge integration plays a mediator role in the effect of internal IT capability on open innovation performance. Meanwhile, the relationship between internal IT capability and internal knowledge integration can be positively moderated by firm social capital. This study extends the research on open innovation and IT business value, and provides theoretical direction for practice.