Deck machinery that is driven by hydraulic motor is a key part for ship exploration in polar area. The reliability of hydraulic motor which works as the key power source of deck machinery is concerned by manufacturers, especially under very low temperature. The low temperature friction characteristics is one of the important factors that influence the reliability of the motor. In this paper, the hydraulic vane motor in deck machinery was taken as the research object. The friction test of the vane head which was made of polyimide (SP21, E.I.Du Pont Company) and the stator, which is made of nodular cast iron(brand is QT350-22L, ISO 1083:2004), was carried out by using the low-temperature tribology tester. Wear tests were performed using a pin-on-disc structure under five different temperatures (-10 degrees C,-20 degrees C,-30 degrees C,-40 degrees C and - 50 degrees C) and three different loads (300N, 450N and 600N) respectively. In order to analyze the wear mechanism of the friction test specimen under different condition, the surface morphology figures of specimen were got by digital microscope system (DMS). The experiment results showed temperature and load have a great influence to the friction coefficient. With temperature decreasing, the friction coefficient does not change linearly, because the mechanical properties of specimen material and the lubrication medium varied significantly in low temperature. Moreover, typical wear and tear patterns are different in different working temperatures. Therefore, the failure mechanism of the hydraulic motor was summarized. The research can not only optimize the design of hydraulic motor, but also provide reference data for the establishment of online intelligent fault diagnosis system of marine deck machinery.