Abstract: The Oedogoniales is a very unusual order of green algae, and the studies about them were mainly focused on their morphological characters. But the relationship between the Oedogoniales and other greens is still hard to guarantee in terms of morphology. During the past few years various phycologists used different characteristics as basis for classification of the genera of Oedogoniales, and the relationship of the three genera was uncertain. In order to clarify the systematics problem existing in this unusual group of Oedogoniales, we collected the samples in a large area, isolated them from field and cultivated them at 20 to 25℃ at a 16: 8-h light： dark cycle under 25μmol photons/m^2·s, in modified of Bold＇ s Basal medium. Algal cultures were harvested by centrifugation at 7400 rpm for 2min and DNA was extracted by CTAB method. The 28S rDNA was newly amplified and sequenced from 8 species representing 2 genera (Oedocladium and Oedogonium) of Oedogoniales. Aligning with another two sequences of this order from GenBank, we succeeded to analyze the sequences covering with all the three genera of the Oedogoniales. Selecting Chlorella ellipsoidea and Fusochloris perforata as outgroups, we constructed a matrix of 38 DNA sequences. The phylogenetic trees were constructed by using Neighbor-Joining, Maximum Parsimony and Bayesian. All the three trees displayed the similar topologic structures. The results showed that the Oedogoniales was monophyletic, and within this order, the genus Oedocladium was mixed in the member of the genus Oedogonium ; whereas the genus Bulbochaete was in a divergence position to the other two genera.