This paper tries to find out the proper way of improving sliver quality through incorporating additional device to existing carding machine. A test is carried out on Model A186F carding machine. Slivers are processed respectively when the machine is in three states: 1) the back plate remains the original state; 2) adding two stationary flats to the back plate; 3) adding a web cleaner (including three stationary flats). The slivers are tested on Uster AFIS fiber tester. The test results show, when incorporating additional stationary flat, if the gauge is improper, it will go against to the improvement of sliver quality; but incorporating a web cleaner will be in favor of improving sliver quality under the condition of big air volume.