Mg/Ca-thermometer is one of the most rapidly developed and as well widely used tools to reconstruct paleo-seawater temperatures in the last decade. There is, however, a growing body of evidence showing that the thermometer is significantly biased by a variety of factors. Of them, salinity effect on Mg uptake into biogenic shell calcites is most recently highlighted, with intensive discussions on the “fidelity” of the Mg/Ca-thermometer in reconstructing paleo-seawater temperature, and in turn in calculating salinity when combining Mg/Ca and oxygen isotope on a same foraminiferal sample. In this article, we reviewed the most recent publications with respect to salinity effects on Mg/Ca-thermometer and summarized solutions and/or methods to correct for salinity effects. The objective of this article is to provide helpful and state-of-the-art references for scientists within the country who are engaged in paleoceanographic study using Mg/Ca-thermometer.