A system and a process for co-producing dimethyl carbonate and ethylene glycol. The system comprises an interconnected ethylene carbonate preparation unit and an ethylene carbonate alcoholysis unit. The ethylene carbonate preparation unit comprises a fixed bed reactor and a light-component stripping column connected to each other. The fixed bed reactor is filled with a supported ionic liquid catalyst. The process comprises the steps of: reacting carbon dioxide and ethylene oxide as raw materials in the fixed bed reactor to produce ethylene carbonate, purifying the ethylene carbonate and then mixing it with an alcoholysis reaction catalyst, and reacting the mixture with methanol in a reactive distillation tower, producing dimethyl carbonate and ethylene glycol. The process increases the conversion rate of ethylene oxide and avoids the need for a process of separating conventional homogeneous catalysts from ethylene carbonate, thereby reducing process energy consumption and simplifying process procedures.