Abstract: Using an engineering example, this paper discusses the method of determining elastic deformation criterion for earth roadbed in detail. It points out that when regression equations need to be established by regression analysis to determine the elastic deformation criterion, two kinds of regression equations which have high reliabilities should be set up by the same measured datas. The independent variable and the dependent variable of one regression equation are respectively the elastic modulus E0 and the elastic deformation l0, but another one's independent variable and dependent variable are l0 and E0 respectively. Which regression equation should be used depends on the relationship between the designed E0 of subgrade and the intersection point P of two curves which are respectively corresponding to the two regression equations stated above. If the designed E0 is less than Ep, the regression equation whose independent variable is l0 should be used，　otherwise the other one should be utilized.

Key words: elastic deformation, checking criterion , earth roadbed