The rheological properties of river sludge mixed with cement and air foam were studied by shear rheological test. The test results showed that under the load the mixed lightweight soil by curing process was similar to the rheological characteristics of hard clay. The soil rheological curve of air foamed soil using river sludge mainly presented three models. When the shear stress level was low, the theological curve appears as attenuation stable; When the shear stress levels continued to increase, the form of the rheological curve was not stable but constant speed type; When the shear stress increased to a certain extent, the rheological curve type was accelerated. With the improvement of the strength of the mixed lightweight soil, the rheological properties of river sludge mixed with cement and air foam is reduced. According to the test, the mixed lightweight soil shear rheological conformed to the seven-component visco-elastoplastic shear rheological model. Using the model can reasonably and reliably describe the rheological process include attenuation, velocity and acceleration of the mixed lightweight soil under various shear stress levels.