The invention belongs to the technical field of chemical catalyst, and in particular, relates to a catalyst for synthesis of glyoxylic acid by glyoxal liquid phase air oxidation and a preparation method thereof. The preparation method comprises the steps: firstly, loading Pd on nano TiO2, then highly dispersing and loading the Pd-loaded nano Pd/TiO2 on activated carbon, and thus obtaining the Pd-TiO2/C catalyst with highly dispersed and stable Pd, wherein the Pd content on the catalyst is only 0.05 to 0.3%. Compared with a Pd/C catalyst with the Pd loading amount of 5%, the Pd-TiO2/C catalyst shows better activity and stability in reaction for synthesis of glyoxylic acid by glyoxal liquid phase air oxidation.