The invention provides a material conveying and automatic feeding and discharging system for processing a main bearing cap. The material conveying and automatic feeding and discharging system comprises three station conveying lines arranged in parallel; the station conveying line in the middle is a manipulator automatic feeding and discharging conveying line; the two station conveying lines positioned on the two sides are manual feeding and discharging conveying lines; a robot station is arranged on the manipulator automatic feeding and discharging conveying line; an automatic feeding and discharging robot is arranged at the robot station; manual operating stations are correspondingly arranged on the two manual feeding and discharging conveying lines; and front side and back side detectionthree-dimensional turntables are separately corresponding to the robot manual feeding and discharging conveying line on one side of the robot station and corresponding to the two manual feeding and discharging conveying lines on sides of the two manual operating stations. Through the reasonable layout of the conveying lines, the way of cooperation of the robot automatic conveying line and the manual conveying lines is adopted, so that on one hand, the operation convenience can be ensured, on the other hand, on the premise of controlling the cost, the processing and production efficiency of the engine main bearing cap is effectively improved.