River bed in the downstream of spillweir of Dangjiangkou Project has produced in tensive scour owing to the effect of fracture properties of foundation rock. For examining the field observation results,the reproductive tests were performed f or river bed scour in the downstream of the dam by using amplified rock block me thod with four kinds of crushed stones of different particle sizes. The results showed that the depths of scour holes in prototype and in model are close to eac h other when the model converted particle size is about 2.25 times larger th an that of prototype.