The work aims to comparatively study the cavitation erosion performance of two materials in RP-3 aviation kerosene and deionized water, analyze the cavitation erosion mechanism and the influence of physical and chemical properties of medium and discuss the feasibility to replace aviation kerosene with deionized water so as to quickly select the anti-cavitation erosion materials used in aviation system. CoCrAlYTaCSi coating was prepared on the surface of cast aluminum alloy (ZL101) by high velocity oxy-fuel spraying (HVOF). Phase compositions of spraying powder, coating and substrate were analyzed by X-ray diffraction (XRD), and morphology and distribution of elements on the surface of materials before and after the cavitation erosion tests were detected by scanning electron microscope (SEM) and the built-in energy dispersive X-ray analyzer. A nano-indentation tester was used to measure the mechanical properties of materials. Avibration-induced laboratory cavitation tester was adopted to characterize the cavitation erosion of CoCrAlYTaCSi coating and cast aluminum respectively in aviation kerosene and deionized water. The corresponding cavitation erosion mechanism was analyzed by overall considering the mean depth of erosion and morphology of two materials after cavitation as well as the physical and chemical properties of two liquid medium. CoCrAlYTaCSi coating was mainly composed of AlCo, Al80Cr20 and Al45Cr7 phases, and all the phases were evenly distributed. Cast aluminum was mainly composed of Al and Al9Si phases, and the enhancement phases were mainly distributed along the grain boundaries. The nanohardness and elastic modulus of Co based coating were about 6 and 2 times higher than those of cast aluminum, respectively. The Al phase inside grains of cast aluminum was firstly damaged, thus aggravating its cavitation erosion process. The damage degree of Co based coating was far slighter than that of cast aluminum because of even distribution of phase and excellent mechanical properties. Its mean depth of erosion in water and aviation kerosene were only about 2% and 1% of those in cast aluminum. The mean erosion depth of two materials in aviation kerosene was less than that in water. The CoCrAlYTaCSi coating shows excellent cavitation erosion resistance in two mediums due to even distribution of phase, higher density, hardness and elastic modulus. Furthermore, this coating exhibits far better anti-cavitation erosion performance in aviation kerosene owing to the different cavitation erosion mechanisms in two liquids.