Herein, a series of metal-free N, P, and Se ternary-doped porous carbon electrocatalysts, referred as "SePNC" as metal-free electrocatalysts, was prepared. This study shows that, the optimal electrocatalyst of SePNC-1050, which prepared at 1050 ℃, has high CO selectivity with Faraday efficiency of 94.8% for CO, and a byproduct of 5.2% H2. After continuous electrolysis for 12 h, the Faraday efficiency and current density remained relatively high, around 95.9% and 80.2% of the initial values, respectively, indicating it has long-term operation stability. This mainly due to the synergistic effect of doped N, P, and Se, as well as the high specific surface area of SePNC-1050 (970.0 m2g−1). This work would provide a good reference to develop high-performance metal-free CO2 reduction reaction (CO2RR) electrocatalysts in future.