The invention discloses a compressor shell cover preassembled flatness detecting and adjusting mechanism and belongs to the technical field of compressor assembling. The mechanism comprises a water flowing platform, water flowing platform positioning mechanisms, photoelectric sensors, a detecting mechanism, an adjusting mechanism, an upper cover plate, a plurality of uprights and a tray, the uppercover plate is arranged above the water flowing platform through the uprights, the detecting mechanism and the adjusting mechanism are arranged on the upper cover plate and positioned on one side close to the water flowing platform, the water flowing platform positioning mechanisms for positioning the tray are arranged at positions, below the detecting mechanism and the adjusting mechanism, of the water flowing platform, and one photoelectric sensor is arranged on one side of each water flowing platform positioning mechanism. The compressor shell cover preassembled flatness detecting and adjusting mechanism is high in detecting accuracy, capable of realizing automatic detecting and automatic adjusting of compressor shell cover preassembled flatness and accurate in adjusting, detecting andadjusting processes are integrated, convenience is brought to streamlined production operation, and compressor production efficiency is improved effectively.