Abstract: Higher plants nitrate uptake systems can be kinetically divided into two systems, one is low-affinity transport system encoded by NRT1 family, and one is high-affinity nitrate transport system encoded by NRT2 and NAR2 families. This review introduces the structures and functions of NRT1, NRT2, and NAR2 proteins, and outlines how the expressions of these genes are regulated by nitrogen sources, pH, and carbon, nitrogen, phosphorus, potassium, and iron statuses.