In the moving bed model test，there may still be some abnormal development of particles of light matirial waves on the basis of meeting the similarity conditions，which affects the resistance similarity and the state of flow and sediment movement. In order to find an effective way to control the abnormal development of particles of light matirial waves，the change of particles of light matirial waves shape under different flow conditions，different particle sizes and different density is analyzed by means of flume test and control variable method. The results show that：under the condition of flow（Fr=0.10~0.32，U/Uc=0.8~2.5），the relationship between U/Uc and the shape of particles of light matirial waves can be expressed more comprehensively by using U/Uc；increasing the size and density of particles of light matirial in a reasonable range can reduce the relative wave height and the ratio of wave length to particle size；based on the Mr.zhan’s formula，the fitting formula of particles of light matirial waves can be established under the condition of this test between Δ/h and U/Uc .