Abstract: Species delimitation is an important part of plant research, but difficult for identification of closely related species. In field investigation and sampling, species are usually delimitated by direct observation of morphological characteristics, but often with bias, leading to delimitation errors. Currently, there is no accurate method for plant delimitation. In this paper, we analyzed two sympatrically distributed oak species, Quercus dentata Thunb. and Q. aliena Blume, using a landmark method, and summarized the species delimitation ability. This method is not only easy but also accurate when compared to the traditional morphologic method. Application of this approach can greatly improve plant species delimitation.