Applying the Riemann-Liouville derivative of factional order theory and the classical model theory,the fractional order of standard linear model for the analytical expression of the shear stress relaxation is given by replacing the traditional Newton dashpot with Abel dashpot.The characteristics of the shear stress relaxation curves of Malan loess are studied based on 9 groups of shear stress relaxation test with different moisture contents under different pressure.Due to the unsatisfied fitting result from using the least squares method for the parameters of fractional order of standard linear model,the Monte Carlo method is used to fit the results.The results show that the shear stress relaxation characteristics of Malan loess can be described by the fractional order of standard linear model efficiently.Based on the fitting results the effective relaxation time and viscosity modulus are determined,and the shear stress relaxation properties is analyzed.