Abstract: Based on field investigation of the depositional sedimentary characteristics of mud-rock flow deposits in 21 key trenches and their basic formation conditions in the Lujiang River (a segment of the Nujiang River) , in combination with the indoor mathematical statistics of the mud-rock flow ditch catchment area and the vertical gradient, the authors used OSL to measure the age of the diluvium. The authors hold that the development of the mud-rock flow has obvious regional and periodic characteristics. The results obtained indicate that, with the Lujiang River as the boundary, the mud-rock flow migrated from the west bank to the east bank, the east bank mud-rock flow grew differently in the north and in the south, and tended to develop from north to south with obvious phases, and the growth of the mud-rock flow can be divided into three phases.