The present invention belongs to the synthesis method of p-hydroxybenzaldehyde. In said method cresol is used as raw material, cobalt chelate is used as catalyst, after having been carried said catalyst can be repeatedly used, and features high activity and good selectivity. The oxidizing agent selects and uses oxygen gas or hydrogen gas, said reaction is implemented in the alkaline solution of anhydrous monobasic alcohol, and one kind selected from inorganic salts of copper (II), cerium (IV) and nickel (II) can be used as catalyst promoter. The cresol conversion rate is greater than 97.0%, and its product yield is 80%-87%, and p-hydroxybenzaldehyde selectivity is greater than 82%, the crude product is recrystallized so as to can obtain p-hydroxybenzaldehyde whose purity is greater than 98%.