Through choosing the developing typical collapse in Tongcheng as the research object

we analyzed the condition of runoff and sediment yield and the discipline of particle size of the different soil layers in granite collapse region under the simulated rainfall experiments. The results showed that the differences between the infiltration rate and accumulative infiltration of the different soil layers were significant in the whole rainfall period; With the extension of rainfall duration

the infiltration rate of the different soil layers decreased at first and then kept stable

and the accumulative infiltration had relatively large difference; The infiltration rate of illuvial horizon was the highest of 328.75 ml/min

which was 1.13 times of that of eluvial horizon

and 1.76 times of that of parent material horizon; Horton model could describe the infiltration rate of the different soil layers well (R2＞0.922)

and the fitting results confirmed the variation process of infiltration rate of the different soil layers under the simulated rainfall conditions. The difference between the sediment yielding rate and cumulative sediment of the different soil layers was significant in the whole rainfall period. With the extension of rainfall duration

the sediment yielding rate of parent material horizon was the highest of 40.43 g/(L·min)

which was 1.79 times of that of illuvial horizon

and 3.11 times of that of eluvial horizon; The cumulative sediment of eluvial horizon increased rapidly

while that of illuvial horizon showed relative slow growth; The cumulative sediment of parent material horizon increased in the whole rainfall period

which was greater than that of eluvial horizon and illuvial horizon. The particles of ＜0.2 mm showed the highest loss in different soil layers

followed by particles of 0.2 to 1 mm

1 to 2 mm and ＞2 mm. With the extension of rainfall duration

the loss of all particle sizes of eluvial horizon decreased gradually

while that of the illuvial horizon gradually increased

and that of the parent material horizon tended to be stable. This study has important significance in theory and practice to reveal the mechanism of runoff and sediment and the research about erosion law of the different soil layers in granite collapse region. The results obtained in this paper set up the basis of the physical model in water erosion process of collapse gully.