Abstract: An investigation on the population density of Rattus rattoides Hodgson on Pingsha State Farm, Pearl-River Delta, Guangdong province was carried out month by month during1963-1966. At our working place, there are mainly three biotopes, namely: the rice field, sugar cane fields and banana fields. The results may be briefly summarized below: 1, There was a little difference of the density of the Rattus rattoides in above three biotopes.