Mud is used to stabilize the borehole wall, and suspend and remove drilling residuals, of which the rheological behavior and hydraulic pa- rameters are very important. This work carried out an experimental study on the theological behavior of bored-pile mud. Formulas of theological parameters were deduced. Borebole-wall stabilization, drilling residual removal and suspension characters of bored-pile mud were analyzed. The results have theoreti- cal and practical significance for evaluating and optimizing bored-pile mud.