Abstract: Due to the shortage of the capillary tube technique,a new laboratory experiment method is established.By using the new method,the boundary layer thickness of the cores in different gradient of pressure has been tested and then the boundary layer thickness plates has been plotted.The research results indicate during the same gradient of pressure,with the increase of the capillary radius,the boundary layer thickness reduced.However,when the capillary radius is larger than 2.5 μm,the boundary layer thickness decreases slowly with the increase of the capillary radius.For the same capillary radius of the cores,when the gradient of pressure is less than 0.2 MPa/cm,the boundary layer thickness increases quickly with the reduce of the gradient of pressure.On the contrary,when the gradient of pressure is larger than 0.2MPa/cm,the boundary layer thickness decreases slowly with the increase of the gradient of pressure.