The existence of big channel in high water cut oilfield leads to rapid process of injected water channeling to the production well, aggravation of invalid circulation, which makes the reservoir flooded quickly and reduces the reservoir sweep efficiency and recovery factor. In order to deepen the understanding of big channel, we determine its parameters, the‘invalid water’, named water flowing in big channel, it is calculated by taking full account of the static and dynamic data of oilfield and using seepage theory. Then, according to the high velocity non-Darcy seepage flow formula and Carman-Kozeny formula, the permeability and pore throat radius of the injection-production well can be calculated. On the basis of mentioned above, taking commonly used reverse-five-spot pattern in the oil field for the example, the permeability and pore throat radius among wells are carried out after splitting the water production according to the theory of fuzzy mathematics. The parameters of big channel in an oilfield are calculated by this new method at last, results show that the new method is accurate and reliable. This study provides theory and data support for effectively block the big channel, and has significant application value.