The “string bead” reflection is one of the important seismic response features in identification ofOrdovician carbonation reservoir in TarimBasin. The mechanism of “string beads” is very complex. Base on forward modeling of wave equation, some different models are designed, and the influence of cave width and height on “string bead” characteristics is analyzed. The result shows that the amplitude of “string bead” intensifies with the cave width increasing, but the length of “string bead” do not change. The amplitude of “string bead” firstly intensifies and then decreases with the cave height increasing , and the“string bead” lengthens. Forward modeling provides approach for further study of response mechanismof cave, cave shape and “string bead” features, and criterion for semi-quantitative and quantitative forecast of carbonate reservoir.