Accurate identification without minimal damage to individuals is need to be surveyed on endangered plants established with more common congener and their hybrid. However, it is difficult to distinguish the hybrid from their parent species only morphology because of the complexity of the hybrid character expression. Using a combination of morphological and cytological approaches for accurate identification and constructing explicit model expressed the morphological differences of species may be useful for subsequent field research. Drosera obovata (2n=30) is a sterile natural hybrid between widespread D. rotundifolia (2n=20) and endangered D. anglica (2n=40). D. obovata is generally well-known to have an intermediate shaped leaf of parent species. However, intermediate characters has not quantified so far. The aim of this study to detect intermediate characters and find quantitative index to identify D. obovata from parent species by establishing a suitable statistical model. Seven morphological characters of 790 Drosera individuals in Sarobetsu mire were investigated. The three species were separated significantly by a canonical discriminant analysis and were readily distinguishable by the leaf blade length and width. Moreover, the ratio of leaf blade length to width was estimated using a Bayesian model accounting for leaf size. The ratio of D. obovata was very intermediate of parent species, and the model assigned nearly all of the D. anglica, D. rotundifolia and most of D. obovata individuals correctly.