Abstract: The popmlation dynamics of Raltus rattoides,a dominant rodent species in farmland in Fujian Province,Was investigated with the systematic catch rates/trap/ night.There were two peak and two valley periods of the catch rate in a year,i.e.April-May and August-September,and February-March and June-July,respectively; and there was significantly negative correlation between the catch rate and acreage proportion of crop appropriate for the damage of this rodent.It is suggested that the effective cavity rate is an available indication reflecting the population dymamics of farmland rodents.