【Objective】 Rosa odorata is an important germplasm resource of Rosa, which has high value of appreciation and utilization. In order to promote the development and utilization of the germplasm resources, the chromosome ploidy, floral synthesis and breeding system characteristics of different R. odorata were studied.【Method】In this study, the chromosome ploidy, pollen vitality, stigma vitality and flower characteristics of 9 R. odorata were observed and determined by flow cytometer and out crossing index, and the breeding system was analyzed. 【Results】 9 R. odorata were identified as diploid, and their flowers were bisexual with bright colors and mostly double or semi-double petals. Male and female flowers of 4 varieties mature at different time. Meanwhile, their pollen vitality was generally low, and the highest pollen vitality was only 35.47%.The out crossing index(OCI) of all varieties was ≥4, and Pollen volume-ovule ratio(P/O) values ranged from 6 709 to 75 521. 【Conclusion】 The combination of out crossing index(OCI) and Pollen volume-ovule ratio (P/O) indicated that the breeding system type of 9 R. odorata was mainly outcross, and the breeding system was affected by many factors, such as the number of pollen grains and petals.