In the development process of oilfields, dynamic data, which is easy to obtain, reflects the connectivity between injection wells and production wells commendably. A set of method has been established in this paper for studying on steam breakthrough channels quantitatively by using dynamic data. Firstly, steam breakthrough wells were identified through curves of watercut and temperature. Then, breakthrough relations were identified with the correlation coefficient method. Lastly, an analytic model, in which pressure and temperature were considered, was established to calculate the breakthrough channel volume. A production well named L31815 in LZ27 block in Henan oilfield in China was systematically analyzed by using the method established. The whole block was further analyzed, and the distribution map of steam breakthrough channels and the breakthrough channel volume were obtained. The results show that the steam breakthrough level around L31513 is serious, while the steam breakthrough level around L31917 is mild. Therefore, steam breakthrough does not only occur limitedly inside a well group, but also sometimes occurs between wells in different well groups. It is proved that the results are credible. The calculation of the breakthrough channel volume provides a theoretical basis for bringing the measures like plugging into operation.