A multi-tube cyclic reactor for synthesizing dimethyl carbonate by liquid-phase oxidization and oxonation is composed of parallelly vertical two or more reaction tube and one reflux tube, separation segment and reflux distribution tubes. The reaction tubes and separation segment are connected attheir lower end. The reflux tube and separation segment are communicated at their bottom. The lower part of reflux tube is communicated via reflux distribution tubes to the bottom of reaction tubes. Heating or cooling jacket is used for reaction and reflux tubes. There are raw material inlet at lower part of reaction tube, material outlet at bottom of reflux tube and one distributor per 1000-5000 mm in reaction tube. The cross-section of reflux tube is 30-100% of total cross-section of all reactiontubes. The cross-section of separation segment is 2-10 times larger than the total one of all reaction tubes. Its advantages are high operation tolerance, mass transfer and efficiency.