Abstract: In order to discuss the universality, influencing factors and strength of preferential flow under the condition of crop, the author did macroscopically objective analysis based on the large amounts of data of 45 automatic soil moisture observation stations which were built in Shandong Province in 2009. The results showed that with precipitation or irrigation quantity increasing, the emergence probability and strength of preferential flow would grow. Under different precipitation or irrigation quantity, the surface soil initial moisture content had different effects on the emergence probability of preferential flow. The emergence probability of preferential flow on different soil texture was sand soil greater than loam, loam greater than clay loam. The research showed that the farmland preferential flow was a universally existent probability event, and the emergence probability and strength of preferential flow were closely associated with soil texture, initial soil moisture content, the precipitation and irrigation amount, and it presented certain nonlinear characteristics.