The invention discloses a feeding and discharging mechanism for two-sided grinding and polishing. The feeding and discharging mechanism for two-sided grinding and polishing comprises a machine frame, a grinding and polishing mechanism, a conveying mechanism, at least three carrying plates, an auxiliary drive and a main drive. The grinding and polishing mechanism comprises two grinding discs. Each carrying plate comprises an outer ring, a sun gear and planetary gears, wherein installation holes used for installing a workpiece are formed in the positions of the planetary gears, and outer gear teeth are arranged on the outer ring. The conveying mechanism comprises two conveying lines. The outer rings of the carrying plates are connected between the two conveying lines at intervals. The outer gear teeth of the outer rings are engaged with the two conveying lines. The auxiliary drive drives the conveying lines to move, and the outer rings are driven to roll and walk through the movement of the conveying lines. A travel switch is used for detecting whether a certain carrying plate travels to a grinding and polishing station or not in cooperation with the carrying plate, and the planetary wheels of the carrying plate located on the grinding and polishing station are located between the two grinding discs. The main drive is in transmission connection with the sun gear of the carrying plate located on the grinding and polishing station. Feeding operation and discharging operation are achieved at the same time while grinding and polishing are conducted through a machine tool, the feeding time and discharging time are shortened, the utilization rate of the machine tool is increased, and the production efficiency is improved.