Abstract: In order to further research the microscopic mechanism of the lignin-modified loess, the pore microscopic characteristics of the lignin-modified loesswithdifferent lignin contents is analyzed based on SEM.Moreover, the variation of microscopic parameters of the lignin-modified loess with different lignin contents is studied based on PCAS.Combined with the unconfined compressive strength test to evaluate the effect of lignin-modified loess. The results show that lignin can effectively fill the pores of loess and enhance the cementation between particles. The content of lignin has a great influence on the microscopic characteristics. Under the curing age of 28 days, the facial porosity, average pore area, pore porosity fractal dimension and average form factor first rapidly decrease and then slowly increase with the increase of lignin content, while the fractal dimension is completely opposite, and the probability entropy of modified loess with the lignin content of 2% and 4% is low. The modified loess with the lignin content of 2%has the highest compressive strength, while too much lignin content will reduce the compressive strength.