In order to improve the calculation method of converted permeability coefficient in karst conduit flow, based on the Izbash’s exponential equation, the formula of converted permeability coefficient for the karst conduit was derived under the condition of considering the local and frictional water-head loss. The rationality of this method was validated by establishing a bent karst-conduit model. Based on this model, the sensitivity analyzing method of single factor was used to discuss the response of converted permeability coefficient to the Reynolds coefficient of current, the diameter and bending angle of karst conduit, and the calculated length of karst conduit, under four flow patterns including the laminar flow regime, hydraulic smooth regime, hydraulic second transition regime and hydraulic rough regime. Two results can be obtained: (a)When the karst conduit is short, the sharp changes of large Reynolds coefficient and flow boundary conditions will produce large local-head loss. Under the condition of considering the local-head loss, the derived converted permeability coefficient is more consistent with the actual situation. (b)The influence of the diameter of karst conduit on the converted permeability coefficient is the largest, while the Reynolds coefficient only has a great influence on the laminar flow regime. The influence of the Reynolds coefficient, bending angle and the calculated length of the karst conduit in other three flow regimes is smaller than that of the conduit diameter.