Abstract: Based on the tests of unsaturated soil characteristics and monitoring data of groundwater levels, this paper takes the landslides in the Heifangtai area in Gansu Province as the research objects, builds a typical slope saturated-unsaturated seepage model, and imitates the influence of fissures on the slope seepage field after the slope irrigation. The influence of the fissures effect on slope stability is studied. The results show that the irrigation water rapidly infiltrates along fissures and it leads to the pore water pressure to rise around the fissures, and the slope stability shows a linear decrease during ten days after irrigation. It is the short-term effect of influence of the fissures on the slope stability. The location of the fissures is much closer to the slope edge and the quantity is much larger. The influence on slope stability is much greater and it is easier to cause landslides along the crack surface. The punning and filling fissures are the efficient path of the control of a landslide.