Abstract: Large moisture prediction models were investigated to study the change law between moisture and strength of loess subgrade.Fredlund & Xing was determined as prediction model of subgrade moisture in loess area according to climate characteristics.Physical parameters of 16 soil samples were tested combined with the prediction model.The results show that mass water content is 16% ~ 19%and volumetric water content is 29% ~3 5%about equilibrium moisture range of loess subgrade,equilibrium moisture ranges of Huohou first-class highway,Ningxia Taotong highway and Jinyang highway were measured in field,the value between the measured and the estimated is about(-1.4 ~ 1.7)%.Optimum moisture content and dynamic resilient modulus of 7 representative soil samples under equilibrium moisture were tested,and the humidity correction coefficient of Shanxi loess subgrade,which the north area is 0.4 ~ 0.5,and the south area is 0.5 ~ 0.6,was recommended.