Abstract: By dividing the fiberglass filter into several layers with different mass thickness, the deposition distribution of α particles sampled in the filter is measured and the relation of the deposition with mass thickness is obtained. The loss rate of detection of α particles with the mass thickness of the filter is measured too, and the selfabsorption of α particles in the filters is determined. The selfabsorption efficiency of α particles in the fiberglass filter with the maximum thickness of 6.7 mg·cm-2 is given. The problems in the test are discussed.