This paper took the soil characteristics between preferential flow and matrix of natural secondary forests at eastern mountainous region in Heilongjiang province as research object. By using the field dye tracer method and Image processing software .The results showed that: The phenomenon of soil preferential flow was very obviously in natural secondary forests at eastern mountain in Heilongjiang province. There were mainly macro pore flow, mean flow and pipe flow. The soil pore connectivity was unimpeded in surface. Water movement process became relatively uniform. So the preferential flow was not easy to occur. Within the range of 10—45 cm soil layer, the dyeing path was no longer a whole uniform diffusion. There was obviously preferential migration and certain surround characteristics. From surface to bottom of soil, the non-capillary porosity of staining region was 0.3%~2% higher than unstained area. Meanwhile, non-capillary porosity was considered as main reason for the generation of preferential flow. In the range of 0—40 cm soil layer, the water holding capacity, capillary capacity and field capacity in the dyeing area were higher than those of unstained area, the soil bulk density was on the contrary. The priority path was most obviously in 20—40 cm of soil in natural secondary forest. In this area, the infiltration rate of preferential flow area was significantly higher than that of matrix. And it proved that the difference of soil characteristic was the main reason of soil preferential flow of natural secondary forest at eastern mountain in Heilongjiang province.