A lifeboat diesel engine lubricating system comprises an oil pump and a machine body. A crank case is arranged in the machine body. An oil sump is arranged at the bottom of the machine body. The lubricating system further comprises a lubricating oil tank and a breathing pipe, wherein the lubricating oil tank is arranged beside the machine body, and the bottom of the lubricating oil tank is provided with a support. The oil pump is a double pump with an oil inlet and an oil outlet which are independent and includes a lubricating pump body and an oil return pump body. The oil inlet of the oil return pump is formed in the bottom of an oil sump cavity, and the oil outlet is led to the lubricating oil tank. A lubricating pump oil inlet is formed in the lubricating oil tank, an outlet is led to a machine filter inlet, and a machine filter outlet communicates with a machine body main oil way. The lubricating oil tank comprises an oil tank cover and an oil tank body. The oil tank cover is provided with a breathing port and an oil adding port. An oil discharging valve is arranged at the bottom of an oil tank body, and an oil level indicator is arranged on the side face of the oil tank body. The engine oil collecting function and the engine oil storage function of the lifeboat diesel engine oil sump are separated, and a diesel engine can normally work when the diesel engine is longitudinally or transversely overturned and inverted.