The invention relates to a polystyrene foam forming body with high foaming multiplying factor and a manufacturing method thereof. The method comprises the following steps: coating rubber resin onto the surface of foaming polystyrene particles to form a coating; sticking the rubber resin on the surface of the polystyrene particles, and then foaming; and obtaining the polystyrene foam forming body of which the foaming ratio is more than 50 times. With the method of the invention, as the surface of the polystyrene foam forming body is coated with a rubber resin layer to strengthen the cohesion thereof, the foam forming body can obtain higher impact strength, higher bending strength, higher elastic recovery ratio and the like even if foaming with 75-90 times of foaming ratio so that the foam forming body having the same volume with the tradition one can be obtained with fewer polystyrene materials so as to save material cost and achieve environment protection benefit.