A portable steady-state rheometer of soil was designed based on the steady shear principle to achieve the portable，rapid，and accurate measurement of rheological properties of paddy soil.The instrument consisted of a parallel-plate rotor measuring fixture，a dynamic torque sensor，a servo motor，and an industrial control panel.A modified formula based on the 3/4R correction principle was derived to correct the non-uniform shear field in the parallel-plate configuration，allowing the measurement of the apparent bulk viscosity of the soil tested.LabVIEW platform was used to develop an upper-computer system to obtain and process data，and achieve two testing modes including steady-state rate sweep and steady-state time sweep.The results of comparative calibration test with laboratory rheometer under the same conditions of shear showed that the designed rheometer had good stability and accuracy in sensing，control，and signal acquisition，and can effectively reflect the constitutive relationship and steady-state rheological characteristics of the soil tested.The results of field test showed that the stress of shear decreased in a power function form with the increase of shear time and gradually approached a stable value under the mode of steady-state time sweep，reflecting the structural breakdown and rearrangement process of soil under continuous shear.The stress of shear initially decreased rapidly with the increase of shear rate and then tended to stabilize under the mode of steady-state rate sweep.The soil exhibited typical characteristics of shear-thinning at shear rate of 70 s?1 and 150 s?1.It will provide a reliable and repeatable experimental approach for investigating the steady-state rheological characteristics of paddy soil.