Abstract: The trace elements (Mg and Sr in this paper) in non-marine Ostracoda could be used as proxies to reconstruct the paleoenvironment of paleo-lake qualitatively or quantitatively. Since their first application to paleoenvironmental reconstruction in the 1980s, great progress has been made in the past 30 years. There are two factors which influence the proxies. One is the changes in M/Ca ratio of the host water (M refers to Mg plus Sr in this paper), including seasonal changes, microenvironmental differentiation and lake evolution process. This type of factors affects the M/Ca ratio in Ostracoda shells through the changes in M/Ca ratio in the host water,and may lead to the increase in error or decrease in reliability of the reconstruction results. The other is the partition coefficient of Ostracoda shells, including M/Ca of host water, temperature, alkalinity and so on, which can directly affect the bio-chemical process of shell secretion and calcification. This type of influencing factors may severely influence the quantitative reconstruction of paleoenvironment. For improving the accuracy and reliability of the results of paleoenvironmental reconstruction, living habits of modern Ostracoda and their trace elements composition in different environments should be carefully studied as reference cases.