Abstract: Based on the CU test results of Malan Loess samples,the stress-strain relationship equation is derived for the constitutional equation of Malan Loess in the framework of the conventional theory of soil mechanics.The theoretical model is used to well simulated the test results for axial strain 115% under different confining pressures furthermore,the model has only two parameters（a and b） and the two parameters can be obtained easily from the conventional triaxial compression test.