Abstract: Paulownia intercropping is a common agroforestry form in the HuangHuaiHai Plain. In the paper, selected 3year Paulownia intercropping field as research plot, and applied plastic film covering and trenching method to treat root, and then measured the length and existing biomass of plant root, soil moisture content in 0-20cm and 20-40cm layers using soil column method. Also, we measured plant standing crop of aboveground by using harvest method. The results showed that: in a certain degree, the plant root growth was affected by intercropping. The effect on aboveground biomass was more obviously. The soil moisture was mainly influenced by precipitation. The distance of trees′ negative effect was approximately 0.7 times of tree height, while for plant root; the effect could be reached to the center of the intercropping field. When the shelterbelt tree was treated by root cutting, the main factor of its negative effect was from tree′s crown; there was no significant difference between on root growth and aboveground biomass under 2 root treatments.