Abstract: In order to investigate the pathogenicity of different infection routes of Riemerella anatipestifer（RA） in meat ducks, in this experiment, firstly, the bacteria were isolated from the brain, heart and liver tissues of clinically RA-suspected infected and dead ducks. Then, the isolated strains were preliminarily identified by morphological characteristics observation, microscopic examination and biochemical characteristics analysis, and the species and serotypes of the isolated strains were further determined by PCR identification and slide agglutination test. Finally, pathogenicity test was performed. The 100 21-day-old healthy Cherry Valley ducks were divided into 5 groups,（drinking group simulated drinking water infection, intramuscular injection group simulated skin wound infection, spray group simulated respiratory infection, contact group simulated contact infection and the control group）; with 20 ducks in each group; they were stocked in 5 different biosafety isolators, respectively. The drinking group was infected with oral bacteria solution for infection（1×10~7 cfu/head）;the intramuscular injection group was injected with bacteria solution at leg muscle for infection（1×10~7 cfu/head）; the spray group was infected with spraying bacteria solution for infection（1×10~7 cfu/head）; the contact group was infected by contact for infection（10 meat ducks were selected for intramuscular injection of bacteria solution, 1×10~7 cfu/head, not account for results; and the other 10 were not treated, account for results）, and no treatment was done in the control group. After 10 days, the survival rate and incidence of each group were counted, and all meat ducks were pathologically autopsied and the pathological features were observed. The results showed that one strain of type 6 RA was identified and isolated. In the pathogenicity test, the survival rates of each group were ranked from low to high as intramuscular injection group（20%）, drinking water group（55%）, contact group（70%）, spray group（80%）, and the control group（100%）. The survival rates of the drinking group, intramuscular injection group, spray group and contact group were significantly lower than that in the control group（P＜0.05）, and the survival rate of the intramuscular injection group was significantly lower than those in the drinking water group, spray group and contact group（P＜0.05）, while the survival rates of the contact group, drinking water group and spray group were not significant（P＞0.05）. The incidences of each group were sorted from high to low as intramuscular injection group（100%）, drinking water group（95%）, spray group（85%）, contact group（60%） and control group（0）. The incidence rates of meat ducks in drinking water group, intramuscular injection group, spray group and contact group were significantly higher than that in the control group（P＜0.05）, while there was no significant difference between intramuscular injection group, drinking water group and spray group（P＞0.05）. There was no significant difference between the spray group and the contact group（P＞0.05）. The heart and liver of the meat duck in the control group were normal, and the other 4 groups showed varying degrees of pericarditis, perihepatitis and balloonitis. Among them, there was less fibrous exudate in the drinking water group, the intramuscular injection group and the contact group; especially in the contact group, that was only a small amount of fibrinous exudate in the pericardium. In the spray group, the pericardium and liver had the most fibrinous exudation, and thicker exudative envelopes formed in the heart and liver. These results indicated that the isolates of type 6 RA strain could infect ducks through drinking water, skin wound, respiratory tract and contact, among which skin wound infection was the most pathogenic to ducks and caused the highest mortality. The pathological features of respiratory tract infection in meat ducks were the most obvious, which could cause serious pericarditis and perihepatic inflammation.