Rock avalanche rock debris caused by rock collapse is very dangerous geological disasters. The debris flow with a sudden can achieve high speed in a very short period of time，and the rocks and detrital material move to a very far distance，the damage and effect range are very great. In order to study the different sizes of rock avalanche flow distance of migration and accumulation characteristics，we have carried out the rock avalanche physical model test of small scale with five different particle sizes of rock detritus dry unconfined particle materials. Experimental results show that under the same test conditions，rock particle size influence on sliding distance and the equivalent friction coefficient is larger. The larger the rock particle size，the greater the sliding distance and pile length，the smaller the equivalent friction coefficient. Five different rock particle sizes are similar of the accumulation form and accumulation width increases along with the increase of particle size. The measured rock particle velocity is greater than the collapse theory calculated value.