The present invention provides a method for producing acryl syrup by bulk polymerization, comprising a step of preparing a mixture comprising monomer component and 2,4-diphenyl-4methyl-1-pentene; a step of heating the mixture to the initial reaction temperature; and a step of adding an polymerization initiator having the half-life of not more than 30 minutes at 5-80° C., wherein the initial reaction temperature is controlled so that the polymerization initiator has the half-life of up to 30 minutes. The method of the present invention has such advantages that reaction runaway does not occur, the control of molecular weight and conversion rate is possible even at low exothermic temperature, and a partially polymerized acryl syrup can also be prepared therefrom.