Gold nanoparticle (AuNPs)-decorated α-Fe2O3 nanorod arrays (AuNPs-Fe2O3) were successfully fabricated by immersing hydrothermal-induced Fe2O3 nanorod arrays into HAuCl4 solution, followed by a simple reduction process. The obtained AuNPs on the α-Fe2O3 nanorods were about 3–5 nm in diameter. The photocurrent of AuNPs-Fe2O3 was twice as large as that of α-Fe2O3 nanorods. Benefiting from the good photoelectric properties, the proposed AuNPs-Fe2O3 can be directly utilized as a self-supporting photoelectrode for nitrite detection. As a result, the as-constructed sensor exhibited good photoelectron catalytic activity and selectivity, high sensitivity (0.1736 ± 0.01 μA μM−1 cm−2) and a low limit of detection (0.07 μM). The current response has a high linear correlation (R ≥ 0.999) in a wide range from 1 μM to 1000 μM and high stability. In addition, the as-constructed sensor was further employed for nitrite detection in tap and rain water samples to evaluate its practical applications.