The invention discloses a passive optical device structural member capable of reducing light reflection, and relates to the technical field of optical fiber communication. The passive optical device structural member comprises a shell, a magnetic ring, a first wedge angle sheet, a second wedge angle sheet and an optical rotation sheet, wherein the magnetic ring is fixedly connected to the inner side wall of the shell, and through cooperative use of a heat dissipation opening, a fixing sleeve, a sliding sleeve, a cover plate and heat dissipation holes, when heat generated by devices in the shell is low, the heat can be effectively conducted into the heat dissipation opening through the through opening and dissipated out through the multiple heat dissipation holes in the side wall of the cover plate, when the heat generated by the devices in the shell is high, the temperature in the heat dissipation opening rises, gas in the fixing sleeve is heated to expand, thrust is generated, the attraction force between the first magnetic block on the side wall of the cover plate and the second magnetic block in the heat dissipation opening is overcome, the cover plate is automatically jacked up, the end opening of the heat dissipation opening is automatically opened, the ventilation area is increased, heat is rapidly dissipated, the self-adaptive heat dissipation adjustment function is achieved, and the heat dissipation efficiency is stable.