In order to study the complexity of pore surface structure of Malan Loess in Lüliang area and its influencing factors, the fractal dimension of pore surface of loess was calculated by mercury injection test and thermodynamic fractal model, and the surface structure complexity of pore in Malan Loess in Lüliang area was quantitatively characterized by this value. The results show that the porosity and mercury removal efficiency are weakly related to the surface fractal dimension, and the larger the porosity is The larger the surface fractal dimension is, the smaller the mercury removal efficiency is, the larger the surface fractal dimension is; there is a linear correlation between the content of micro pores (pore diameter less than 1 μm), the surface area and the surface fractal dimension. The higher the pore volume content and the surface area are, the larger the surface fractal dimension is; the linear correlation between the median pore diameter and the surface fractal dimension is, the smaller the value is, the larger the surface fractal dimension is . It can be seen that the micro pore content will increase the complexity of the whole pore surface.