Study of the relationship of rodents density with forage loss is essential both for the calculation of economic injury levels (EIL) and for management decisions. An experiment was conducted to investigate rodent density and aboveground biomass of forage in typical steppe in Inner Mongolia each autumn from 2012 to 2016,. Rodents were live-captured and forage biomass was measured with a quadrat method. Rodent damage was estimated using the density and daily intake of rodents to determine forage loss. The results suggested that: (1) a three-parameter sigmoid curve modeled the relation between rodents density and forage loss, which was better than that of other models, and the formula was: Loss=k/(1+e ^a-rdensity). (2)The largest forage loss (=23.30%) occurredwhen the rodents density was greater than 906 standard rodent units per hectare. (3) Based on our optimal model, the damage threshold was 174 standard rodent units per hectare in typical steppe.