This study was conducted to explore the effects of dietary mannose oligosaccharides (MOS) on the reproductive performance of Bashang long-tail breeding hens and maternal antibodies of their chicks. A total of 2 400 Bashang long-tailed breeding hens of 273-day-old were selected and randomly divided into 4 groups (test groups 1 to 4), and supplemented with 0, 0.5, 1.0 and 2.0 g/kg MOS in the basal diet, respectively. Each test group had 3 replicates and 200 chickens in each replicate. The artificial insemination technology was used and the test period was 35 days. The breeding eggs were collected on the 31^th day of the experiment for 5 days, and the laying rate, feed to egg ratio, qualified breeding egg rate, fertility rate of hatching breeding eggs, hatching rate of fertilized eggs and dead embryo rate were calculated; the number of Escherichia coli and Salmonella in the inner membrane of dead chicken embryo eggshell were detected after hatching; and the serum antibody titers of Newcastle disease and bursa of Fabricius of chicks at 1-day-old were measured. The results showed that, compared with the test group 1, the laying rate, qualified breeding egg rate, fertility rate of breeding eggs and hatching rate of fertilized egg were extremely significantly increased (P<0.01), the feed to egg ratio and the dead embryo rate were extremely significantly decreased (P<0.01), the broken egg rate was significantly decreased (P<0.05), the Escherichia coli number in the dead embryos was significantly decreased (P<0.05), and the antibody titers of Newcastle disease and bursa of Fabricius of 1-day-old chicks were also showed an upward trend (P>0.05) in the test group 4. These results indicate that the dietary MOS can enhance reproductive performance of Bashang long-tail breeding hens, improve the hatchability of hatched breeding eggs, increase the antibody titers of Newcastle disease and bursa of Fabriciusc, and reduce the Escherichia coli infection in the chicken embryo. The best effect is obtained by supplementing 2.0 g/kg MOS in the diet.