Abstract: We studied the meterials by multiple regression analysis,the data were yearly rainfall,season rainfall,yearly average density of Meriones unguiculatus,monthly density of Apr.to May,Oct.to Nov.in the period 1981-1993 in the desert-grasslands in Erdosi.The conclusions were as the following:(1) Yearly rainfall especially in June to Aug.was a main factor affecting M.unguiculatus population density.(2) The spring density next year could be forecasted by the autumn density this year and the rainfall of four seasons.And also,the autumn density could be forecasted by the spring density and the rainfall of four seasons.