The invention discloses a polystyrene supported type catalyst and an application method thereof in synthesis of dihydrocoumarin; the polystyrene supported type catalyst is used for catalyzing 1-indanone to synthesize a lactone compound and particularly includes the following steps: adding 1-indanone and an organic solvent into a container, dropwise adding a hydrogen peroxide solution and the polystyrene supported type catalyst, and carrying out a stirring reaction, after the reaction is finished, precipitating the catalyst with ethanol, centrifuging the reaction solution, extracting the supernatant, washing, and distillating to obtain dihydrocoumarin. The polystyrene supported type catalyst has the advantages that with use of the polystyrene supported type catalyst, the preparation method is simple, the 1-indanone conversion rate is increased, the atom utilization rate of the reaction is improved, moreover, the polystyrene supported type catalyst is reused, no waste acid is treated, and the polystyrene supported type catalyst has the characteristics of energy saving, emission reduction, good selectivity, high atom efficiency, mild reaction conditions, environmental cleaning and the like, and is suitable for industrial engineering application.