A pot experiment was conducted to study the root morphological characteristics, root absorption area and nitrogen use efficiency of poplar seedlings under the four treatments of CK (neither urea nor vermicompost was applied), CF(100% of nitrogen was provided by urea), VC(100% of nitrogen was provided by vermicompost), and VC+CF(50% and 50% of nitrogen was provided by vermicompost and urea, respectively). Results showed that in comparison with the CF treatment, the VC+CF treatment significantly increased the total root length, root surface area, root volume and the number of root tips, but obviously decreased the root average diameter. The total root length in the VC+CF treatment was increased by 161.70%, 52.80% and 14.79% in comparison with the CK, CF and VC treatments, respectively. At the same time, the VC+CF treatment dramatically increased the total absorption area and active absorption area of root system. Not only the dry matter accumulation of root, stem and leaf, but also the absorption amount of nitrogen, phosphorous and potassium was remarkably enhanced by the use of VC+CF. Furthermore, the nitrogen use efficiency was 59.07% in VC+CF treatment, indicative of 57.35% and 27.09% increases over the CF and VC treatments, respectively. Additionally, the growth rate of aboveground was significantly faster than underground owing to the application of fertilization. However, in the VC treatment, less effect on root morphological characteristics, root absorption area and nitrogen use efficiency of poplar seedlings was observed than that in the VC+CF treatment. In conclusion, vermicompost co-applied with inorganic fertilizer had better effect on root characteristics and nutrient uptake of poplar seedlings.