Abstract: For even distribution of strips in case, the effects of the spreader mechanism movement, in terms of stroke, reverse frequency and central position of movement, on sampling volume and density variation ratio (DVR) in strips case were investigated. The air cylinder's running was controlled by a pressure reducing valve and of strips was determined by the 9-point method. The results showed that:when the stroke was of 75 mm, the central position was at the place where air cylinder extended out for 175 mm and the working pressure was from 0.1 to 0.15 MPa, the DVR was less than 12% during test.