In our previous study, we found two rbcL types (JN and JS types) in Japanese Conocephalum japonicum Grolle. In this study, we collected plant materials from 20 localities in China, Korea and Taiwan. We determined 1304 bps of each nucleotide rbcL sequence and found two rbcL types in Asian C. japonicum. One of them was a new rbcL type (CS type), which differs from the JN and JS types by 10 and 8 nucleotides, respectively. The CS and JS types were found both in Mainland China and Taiwan. We could not find any morphological differences between the two types. In Chitou, Taiwan, the two rbcL types were growing together within a small research area measuring 100m×200m. We performed an allozyme analysis on this population and observed that the CS type had Est-4a and Tpi-la alleles; whereas the JS type had Est-4b and Tpi-1b. It was strongly suggested that these two rbcL types might be reproductively isolated cryptic species of C.japonicum.