The invention provides a method for synthesizing unsaturated polyester resin for artificial marble, which mainly comprises the following steps of: (A) putting unsaturated dibasic acid, unsaturated dibasic acid anhydride, dicyclopentadiene and partial dihydric alcohol in a reaction kettle, heating and performing reflux reaction under the protection of nitrogen, and then heating and performing reflux reaction until a certain acid value is reached; (B) changing the state of the system to a distillation state, adding the residual dihydric alcohol to perform polycondensation reaction, and evacuating to discharge water forcibly when the water discharge quantity reaches 85% to 90% of a theoretical quantity, so that the reaction continues to be below the certain acid value; and (C) lowering the temperature and adding a polymerization inhibitor, diluting with styrene, and cooling and filtering to obtain the finished unsaturated polyester resin. The method provided by the invention is steady and controllable in the reaction process, fast in polycondensation reaction and small in quantity of generated waste water, and the obtained product has the characteristics of steady and slow curing andheat release at normal temperature, small rate of curing shrinkage, excellent boiling water resistance and the like, and can meet the quality demand of the artificial marble.