Boundary-fitted calculation methods have traditionally used the generalized coordinate system which is required the condition that the coordinate axes intersect. When meandering formation extremely develop, the channel eventually is short-circuited. Because of this, general coordinate system should not be applied to evaluate that problem. This study proposes a new boundary-fitted calculation method that combines a co-orthogonal coordinate system and a boundary-fitted cell system. To validate the accuracy of this method, it was applied to reproduce the flow regime of a meandering channel measured in a previous flume experiment. The calculation method was generally successful at reproducing the flow velocity distribution.