The SPX gene family includes four subgroups: SPX, SPX-EXS, SPX-MFS, and SPX-RING, which play an important role in phosphate sigal response, but so far, little is known about the functions of this family in wheat. Previously, we identified a gene TaSPX1 (GenBank No. Ak332300), belonged to SPX subfamily from wheat (Triticum aestivum). Subcellular localization analysis showed that it targeted onto nucleus. Phylogenetic tree of TaSPX1 and its homologous proteins from the wheat, Arabidopsis, and rice SPX families showed that it was closely related to OsSPX1, a member of rice SPX subfamily. The relative expression level of TaSPX1 significantly increased under low nitrogen (low-N) stress when investigated by RT-qPCR. Transgenic tobacco (Nicotiana tabacum) overexpression lines were generated. Using the culture methods of Murashige & Skoog (MS) hydroponic solution, the phenotype of WT and OE under low-N stress treatment was investigated. We found that the plants of OE3 and OE4, two OE lines overexpressing TaSPX1, displayed increased growth vigor and leaf area, together with the enhanced plant fresh weight and root weight, and elevated photosynthetic parameters including photosynthetic rate (Pn), Intercellular carbon dioxide concentration (Ci), stomatal conductance (Gs), and transpiration rate (Tr), along with the increased contents of nitrogen, soluble sugar, soluble protein, and chlorophyll content upon low-N stress with respect to WT. Studies on transport and assimilation related parameters showed that under low-N stress, the relative expression level of some related genes and the activities of nitrogen assimilation-related enzymes were increased. Assays on the SOD, POD, and CAT, the enzymes functional as cellular protector, revealed the higher activities of them in OE plants than those in WT. On the contrary, MDA content was decreased. Further RT-qPCR analysis indicated the expression levels of several protection enzymes mentioned above were higher in OE plants than those of WT under low-N stress. Therefore, TaSPX1 played an important role in mediating plant resistance to low-N stress by improving photosynthetic parameters, enhancing nitrogen absorption and transport, and strengthening the protective enzyme system. The results enrich new understanding on the function of wheat SPX family members involved in abiotic stress, and provide a theoretical basis for genetic improvement of crops against low-N stress.