Abstract:As a special property of loess permeability, percolation of loess seepage involves the special problem of loess permeability mutation. Research on influence of the pore size distribution of loess on seepage characteristics can provide some theoretical basis for the seepage problems in engineering and the practice value, however, this part is often neglected in previous studies. this paper carried out a set of intact loess and the experimental study of two groups of remodeling loess: seepage phenomenon in the process of loess seepage was analyzed by using variable water head test, and then three sets of sample to make use of nuclear magnetic resonance (NMR) technology evaluation of pore distribution, and final analysis for the loess seepage pore size distribution over the influence of seepage characteristics. The experimental results show that: (1) due to the good original structure of the undisturbed loess, the distribution of pore size is more concentrated than that of the remolded loess, with the pore size concentrated in the middle of 0.011~ 0.11 μm. Due to the loss of the structure of remolded loess, some soil particles will produce cohesion, resulting in an increase in the proportion of micropores and macropores in the soil.(2) because the pores of undisturbed loess are more concentrated and the internal pores are less permeable, it is easier to reach the critical state, which leads to a rapid decline in permeability. The critical water head of undisturbed loess is higher than that of remolded loess with the same dry density. The higher the dry density, the lower the porosity, the smaller the pores and the higher the critical head. In this paper, the effect of pore size distribution on seepage percolation of loess is analyzed for the first time by using convenient and fast nuclear magnetic resonance (NMR) technology.