Root system plays an important role in uptake of water and nutrients by Poplar trees. Understanding the coupling effect of water and nitrogen on the morphology and distribution of fine roots will assist in making efficient water and nutrient management strategies for fast-growing and high-yield Populus×euramericana cv.‘Guariento’ plantations. In this study, drilling method is used to investigate the morphology and distribution of fine roots in 0-30 cm soil layers in a young poplar plantation under the surface drip irrigation and fertilization technology. The trial includes nine treatments, which were different combinations among three irrigation treatments (drip irrigation was initiated when soil water potential (ψ_soil) reaches -75, -50,or -25 kPa) and three fertilization treatments (nitrogen application rates are respectively 150, 300, or 450 g tree^-1 a^-1). A control non-irrigation and non-fertilization treatment (CK) is also included. Results showed that, for the vertical direction, the biomass, surface area, the volume and length density of fine roots were significantly decreased with increased soil depth in all treatments. In -50 and -75 kPa treatments, specific root length in 0-10 cm soil layer is significantly lower than those in 0-10 and 20-30 cm soil layers. Whereas, in -25 kPa and CK treatments, no significant differences in root length density are detected among various soil layers. According to the distribution of most fine root parameters, the vertical distribution pattern of fines is not affected by the interaction between water and fertilizer. Fine roots were mainly distributed in 0-10cm, where the biomass and root length density was 1.25-5.05 and 1.05-2.05 times as high as that in 10-20 cm, and 2.80-13.06 and 1.99-4.99 times as high as that in 20-30 cm. The biomass, root length density, surface area and volume of fine roots in the three irrigation treatments were significantly larger than CK under middle and high fertilizer level, but this was not found under low fertilizer level. Especially, fine roots biomass under both high water and fertilizer level, which significantly promoted the growth of fine roots best. Compared with CK, the fine roots biomass of three soil layers were significantly improved 326%, 386% and 442%, respectively, and the root length density was significantly increased by 345%, 176% and 176%, respectively. Each water and fertilizer treatments showed that the amount of specific root length decreased as the amount of drip irrigation and fertilization increased. Fine root biomass changed with the fertilization varied by a regression equation which was fitted with high a value of R²(0.702-0.891), under the same fertilization level in each soil layer but was fitted with low relationship under the same drip irrigation in each soil layer. It illustrates that the response to the coupling effect of water and fertilizer of fine root growth and distribution has a stronger trend to fertiliertaxis than hydrotropism of poplar plantation.