Electrochemical and electrogenerated chemiluminescence (ECL) properties of a glassy carbon electrode modified with US nanotubes (CdS-GCE) are investigated in neutral media. The cyclic voltammogram (CV) shows two cathodic peaks (P-C1 and P-C2) at -0.76 and -0.97 V and an anodic peak (P-A) at -0.8 V, while two ECL peaks around -0.76 V are observed. Similar mechanisms of both ECLs are supposed and possibly related to the capture of an electron at a surface trap, that is, the Surface sulfide vacancy (V-S(2+)) of US nanotubes and its electrocatalytic reduction to H2O2 generated from the dissolved oxygen. P-C2 and P-A are ascribed to the two-electron redox at V-S(2+). Moreover, electrocatalysis to nitrate reduction is also found at P-C2, with a good linear relationship between nitrate concentration and electrocatalytic peak current in CV.