The microstructure of loess mainly reflects the size distribution, orientation, contact mode and pore distribution of particles. The six original loess (low clayey silt loess) on the same site in Lanzhou is selected by the direct shear test, high power electron microscope and energy spectrum test. To simulated calculation the cohesion (C) and internal friction angle (φ), used by the parameters data, including to the mineral element (Fe/Al/Si, Al/Si, K) ratio, microstructure parameters (Long axis of the particles, long axis’ skewness, kurtosis and orientation degree. The results indicated that the (φ) value was linearly correlated with the mean value of the Angle, and the correlation coefficient of the fitting formula was 0.82. The cohesion C value was linearly correlated with the kurtosis, Skewness, Fe/Si, Al/Si and K/Al of the long axis, and the maximum correlation coefficient after fitting was 0.99. The fitting formula of microcosmic parameters and shear strength can provide a new research method for predicting the shear strength of loess samples.