The process for synthesizing pyruvaldehyde by catalytic oxidation of 1,2-propanediol features use of Ag catalytic dressing method, where dressing agent is a compound mainly containing Zr, Zn, P and K, addition of 10-30% water in reaction materials, 500-650 deg.C reaction temp. and tail gas recirculation. Its advantages include high transform ratio of propanediol (about 100%) and selectivity of pyruvaldehyde (up to 75%), and low cost.