Pyridine nitrogen in nitrogen-doped materials is considered to be the most active nitrogen catalytic site for electroreduction of CO₂ to CO. Dicyandiamide (DCDA) was used as nitrogen source and carbon oxide nanotubes (CNTs-O) as dispersant to prepare nitrogen-doped carbon/carbon nanotube mesoporous composite catalyst with rich pyridinic nitrogen via electrophoretic deposition-calcination method. By changing the mass ratio of DCDA and CNTs-O, the composite catalysts with different contents of g-C₃N₄ were synthesized. Based on a series of characterization and electrochemical tests, it was determined that CN_0.5/CNTs catalyst prepared at DCDA/CNTs-O mass ratio of 0.5 exhibited the best electrocatalytic performance for CO₂ reduction to CO. The Faradaic efficiency (FE) of CO on CN_0.5/CNTs at −1.0 V vs. RHE was as high as 94.1%, and the current density of CO generation was −13.27 mA/cm2 . The FE of CO was still maintained at a high level (>85%) after 24-h long-term electrolysis.