Abstract: A novel method was reported for the synthesis of glyoxylic acid from glyoxal oxidized by O₂ under the catalysis of NO_n （n=1,2）. A possible reaction mechanism was proposed. Under the optimized reaction conditions （catalyst 0.13～0.15 mol（per mole glyoxal）, mass fraction of glyoxylic acid 25%, Lewis acid 0.11～0.13 mol（per mole glyoxal）, 40～50 ℃, 0.5 MPa）, a good result was achieved with the conversion 98.7%, selectivity 79% and yield 78%. Compared with the industrial method using nitric acid, the present contribution is more safe, economical and less contaminating the environment.