The invention provides a method for directly preparing propylene carbonate. The method adopts CO2, O2 and propylene as raw materials, and is characterized by comprising the following steps: (1) introducing O2, propylene and CO2 into a reaction kettle in which metalloporphyrin, a compound surfactant and trimethylbenzene are arranged for reaction, wherein the use amount of metalloporphyrin is 0.001-0.02% of the total weight of propylene and CO2, the compound surfactant is a mixture of sodium dodecylbenzene sulfonate and Tween 80, the use amount of the mixture is 10-15% of the total weight of propylene and CO2, trimethylbenzene is used as a solvent, the use amount of trimethylbenzene is 200-400% of the total weight of propylene and CO2, and the reaction kettle is in a sealed state; (2) reacting for 3-4 h at 120-130 DEG C; (3) placing the reaction kettle in an ice water bath, and stopping reaction. Through the preparation method, the largest reaction yield can reach 95%.