With the aim to establish the relationship between soil surface porosity and surface roughness,a fractal analysis procedure based on 3-D surface area calculation was proposed, which applied a surface unit to cover the soil roughness characteristics. Using the soil surface unevenness data measured by a laser profiler, the method could derive the fractal dimension of soil surface directly (D∈[ 2,3)). Furthermore, 3-D surface area method was also introduced into multi-fractal spectrum analysis for investigating fine scale information. The statistical analysis demonstrates that fractal dimension Dl, Dr, and multi-fractal parameters α|fmax, Δα can reflect the change process of soil surface roughness effectively regardless the influence of different tillage types. In this case, α|fmax fitted a linear relation to porosity with the value of R2= 0.7014, which showed potential to be a meaningful indictor for surface porosity estimation.