Abstract: The effect of velocity on temperature field and stratification in density lock was studied through experiment. A new zone model was proposed. The results show that fluid in density lock can be divided into three zones including mixing zone, stratification zone and constant temperature zone. The stratification zone can be divided into strong stratification and weak stratification, and the interface is located between the mixing zone and the stratification zone. Additional, the temperature field of density lock is divided into five categories in which the second class is the best for normal work.