A reactive distillation (RD) process with a gas-phase side reactor potentially promoted by in-situ hydration is proposed to overcome the thermodynamic restriction of direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. A homogeneous RD model with fixed bed reactor is established in gPROMS platform. The feasibility of the process for direct DMC synthesis is analyzed. The important configuration parameters (e.g., side withdrawal stage and recycle stage) and operating conditions (e.g., reflux ratio and feed ratio) of the RD process are systematically studied. In-situ hydration of ethylene oxide occurring only in the column is introduced for further enhancement. With the process intensification, the conversion of methanol is both improved from approximately 10% in a one-step reactor to 99.5% of RD with and without EO hydration.