Abstract: Oryza sativa subsp. japonica cv. Nipponbare with genome size was used as the internal standard; with the tender leaves of Camellia oleifera as materials, a suitable method of flow cytometry analysis was screened to estimate genome sizes of C.oleifera. The findings indicated that after the repeated screening of the dissociation solution, the improved Otto method had the best dissociation effect on the nuclei of C.oleifera, with which the coefficient of variation (CV) was controlled within 6% using the internal standard rice and the tested sample; samples could be tested on the machine after the liquid was added to them with PI staining agent for 10 minutes. The genome sizes of the 15 C.oleifera varieties ranged from 6 411.99 to 9 398.58 Mbp. There were significant differences among the examined varieties.