Abstract: The research of effect of grid on stratification stability in density lock is carried out,through the theoretical analysis and experimental observation on the flow field in density lock.The results showed that,the flow in density lock is eddy flow;eddy flow is limited to the top of stratification when the stratification exists;the eddy and stratification interacted with each other until equilibrium,there are more than one equilibrium points in density lock without grid,the stratification is hard to stabilize because it will transit to next equilibrium point easily,but it easy to reach stable with the grid,and the stratification interface will higher with grid than without grid because the grid enhanced the energy dissipation.