Abstract: The authors have observed and studied the ecology of Lesser Bamboo Rat (Cannomys badius Hodgson),in March,April,1985 and July,1986,including its morphological characters,the structure of the tunnel system,foods,reproduction and behavior.The Lesser Bamboo Rat distribute in Yingjiang,Ruili,Menglian Yunnan province,China.The Lesser Bamboo Rat is a typical animal living undergroud.They stay in the mountain slope of rubber plantation,bush,broadleaf forest and vegetable garden,stay in tropic and subtropic zones from 300 m to 950 m.The structure of the tunnel system of the Lesser Bamboo Rat is rather complex,including hillocks,food gathering tunnels,nests and refuging tunnel,with a total length as 14.7 to 57.5 m.Important food of the Lesser Bamboo Rats are roots and stems of Thysanolaena maxima and Arundo donax,and roots of Hevea brasiliensis.They may eat Bambusa multiplex,Imperata cylindrica,Castanopsis spp.,Lithocarpus spp.,Lophatherum gracile,Colocasia esculenta and Musa wilsonii 18 species plants.Sexual maturity of the Lesser Bamboo Rat is about 1 year,birth season is from 3 to 5 months in Yingjiang,Yunnan,gastation period,about 40-43 days,the number of young,2-3.