The invention discloses a shipborne diesel engine power generating unit protecting and parallel operation controlling device which comprises an alternating-current signal conditioning circuit, an alternating-current voltage signal conditioning circuit, an A/D conversion circuit, a sine wave and square wave conversion circuit, an analog quantity output circuit, a switch quantity input circuit, a switch quantity output circuit, a communication interface circuit, an external order input circuit, a display driving circuit, a display and a main controller. Output ends of the A/D conversion circuit, the sine wave and square wave conversion circuit, the switch quantity input circuit and the external order input circuit are all electrically connected with an input end of the display driving circuit, a control output end of the main controller is electrically connected with input ends of the analog quantity output circuit, the switch quantity output circuit and the display driving circuit respectively, and the communication interface circuit is electrically connected with the main controller bidirectionally. The shipborne diesel engine power generating unit protecting and parallel operation controlling device integrates various functions like data collecting, power generating unit protecting, automatic synchronizing parallel operation controlling, displaying and communicating, and is especially suitable for automatic control systems for power generating units of ship power stations.