North Pacific Intermediate Water (NPIW), one of the key components of global meridional overturning circulation, plays an important role in regulating regional oceanic environment and global climate change. In this study, we review the state-of-the-art of NPIW evolution and its effect on climate change. We suggest that the NPIW is very sensitive to the response of global climate change. Moreover, climatic signal in high-latitude can be propagated to the low-latitude in the North Pacific through NPIW via the "oceanic tunnel". On the other hand, East Asian Summer Monsoon can also exert influence on the formation and composition of NPIW through affecting the precipitation in the drainage basin and subsequent runoff of the Amur River to the Okhotsk Sea. On millennial time scales, the ventilation seesaw occurs between the NPIW and the Atlantic Meridional Overturning Circulation (AMOC), which is associated with the variations, induced by AMOC, in sea surface temperature and salinity. Both physical and biological processes related to the changes in the NPIW could have contributed to the fluctuations of atmospheric concentrations of CO_2 over glacial cycles.