The invention relates to a green synthetic reaction device for preparing epoxypropane through a direct oxidation method. A tube nest type reactor is adopted as the reaction device. The reaction device is characterized in that reaction tube nests (5) of the reaction device comprise hollow tubes (5.1), a metal fin (7) is arranged at the central axis (6) of each hollow tube (5.1), the outer edges of the metal fins (7) make close contact with the hollow tubes (5.1), the two ends of the metal fins (7) are perpendicular lines, and the middles of the metal fins (7) are shaped like helical twisted strips. According to the green synthetic reaction device, heat generated in reacting is quickly transmitted into heat transfer media arranged outside tube bodies through the metal fins and the tube bodies of the reaction tube nests, and the heat dissipation speed is high; the heat exchange area can be increased through the metal fins which are helically arranged; through holes can enable reaction liquid to generate convection flows and turbulent flows, the temperature of the reaction liquid is uniform while the heat exchange efficiency is improved, and the product quality is stable.