Large-scale of stone in CHI-TOU watershed in NTU experimental forest became flexible after the 921 earthquake in 1999, which caused serious disaster in the central section of Taiwan. Flexible soil leads to expand the narrow holes and small ditches. The expansion of the cracks were worsened by the attacks of several typhoons and therefore have become highly harmful to the downstream communities. The main purpose of this study is to investigate on debris-flow crack from top reaches to the bottom in the Shen-Mu crack of CHI-TOU. By measuring the horizontal and vertical sections before and after typhoons in July 2004, Oct 2004 and Oct 2005, and analyzing the mass movement in the crack, the effect of the projected constructions in the crack will be assessed. Especially taking the advantage of comprehensive considerations on the particle-size distribution, it is helpful for the prediction and resolution of future debris-flow disasters.