Abstract: In order to study the entrained vortex flow and get the influence of the structure of the intake on it,the 3-D-PIV technique is used to measure this kind of flow near the horizontal intake.The image of the particles got by 3-D-PIV experiment in two media is unclear for the difference of refractivity in different media.So the refractivity-revised method is used to solve the problem.And the multi-step calibrated method is used to improve the measurement precision of the w vector.In the experiments,the distributions of the 3-D velocities of the entrained vortex are obtained.The relation between the entrained vortex and the structure of the intake is also found.Results show that the intake with 30° angle chest wall can prevent the entrained vortex effectively than that with 0° angle chest wall,so it is a good idea,through changing the angle of the chest wall,to prevent the entrained vortex near the intake.