Determine the frequency, timing, ploidy levels, and possible nature of polyploidizations in considered genome. Using the API, we clarified the polyploidizations in Oleaceae. We first selected the excellent eudicot reference genome grape (V. vinifera) to examine the polyploidizations in Oleaceae. Then, by inferring the anchored genes and synteny blocks among these genomes, we found that the number of syntenic genes within S. oblata, O. europaea, and F. pennsylvanica is higher than that of J. sambac (details in Diagram). This suggest that the S. oblata, O. europaea, and F. pennsylvanica underwent another round of WGD after their divergence with J. sambac. Further, according to the BBK-Dotter produced synteny dotplots, we found that the orthology ratios are 1:3 between the genomes of V. vinifera and J. sambac, 1:6 between the genomes of V. vinifera and O. europaea, 1:2 between the genomes of J. sambac and O. europaea, and 1:1:1 between the genomes of S. oblata, O. europaea, and F. pennsylvanica. Phylogenetic analysis of the 367 synteny-based orthogroups between the V. vinifera and four Oleaceae genomes, we found that 6.1% (11/179) gene trees also support the genomic orthology ratios. These results clearly revealed that a common hexaploidization (OCH) in all Oleaceae plants and a tetraploidization (OCT) shared by S. oblata, O. europaea, and F. pennsylvanica. Our results are consistent with the studies of J. sambac and S. oblata, rather than a single hexaploidization or two common tetraploidizations in all Oleaceae plants. Using our developed computational model to perform Ks distribution statistics and evolutionary rate correction on OCH- and OST-generated paralogues, we infer that OCH occurred at ~53-61 Mya coinciding with the Cretaceous-Tertiary mass extinction event and OST occurred at ~18-21 Mya. Using the P-index-calculator, we compared the fractionation levels (FLs) of OCH and OST producing subgenomes, with P-index values of 0.52 and 0.33, respectively. According to the previous reports, a P-index value greater than 0.3 indicates significant divergence in the FLs of subgenomes, and its association with WGD may originate from ancient hybridization.