Abstract: This study investigates the formation mechanism of the mixed layer in the Chukchi Sea in summer of 2019, utilizing multi-source high-resolution CTD data. The mixed layer depth (MLD) is determined using a fixed threshold method with a threshold criterion of 0.1 \mathrmk\mathrmg/\mathrmm^3 , and the main factors influencing the MLD are studied with correlation analysis and multiple linear regression. The results indicate that the 0.1 \mathrmk\mathrmg/\mathrmm^3 threshold criterion provides a more accurate estimation of the MLD in the region. Salinity predominates in density formation in the Chukchi Sea, exerting a significant influence on the MLD. Furthermore, by comparing the impacts of wind, momentum flux, and buoyancy flux on MLD in three areas, we found that in northern Chukchi Sea, the MLD is predominantly influenced by wind and momentum flux, whereas in southern region, buoyancy flux has the most significant impact on the MLD. Additionally, in northern Chukchi Sea, the synergistic effect of momentum flux and buoyancy flux contributes the most to the MLD. The influence of stratification and wind on the MLD varies across different regions. In northern Chukchi Sea, wind has much greater impact on the MLD than stratification, contributing 38% and 9%, respectively. In the other two regions outside northern Chukchi Sea, wind and stratification contribute almost equally to the MLD.