The development of efficient catalysts for NO electrocatalytic reduction (NOER) is an effective way to synthesize ammonia and solve environmental pollutants. Now, Pt, Au and other metal surface electrocatalysts still have great challenges for the practical application of NOER due to their high cost. However, using single-atom catalysts (SACs) of low-cost and high catalytic activity to study NOER is relatively rare. Herein, based on firstprinciples methods, the catalytic performance of a series of transition metal supported on the pure 1T-SnSe2 monolayer for NOER is systematically studied in this paper. The calculation results show that Sc, Ti, Y, Zr and Hf atoms can stably form SACs on 1T-SnSe2 monolayer, and the N-O bond can be successfully activated when NO is adsorbed. In addition, the Zr supported 1T-SnSe2 monolayer (Zr@SnSe2) has a high catalytic activity for NOER, with a low limiting potential of 0.11 V. Moreover, it is noteworthy that Zr@SnSe2 inhibits the occurrence of hydrogen evolution reaction (HER). We hope that our work will not only provide a new idea for designing efficient catalysts of NOER, but also provide an effective method to solve the problem of NO environmental pollution.