Abstract: To investigate the axial transport law of cuttings bed in the horizontal section of long horizontal wells during rotary drilling, cuttings transport experiments of horizontal wells were conducted based on the differential pressure method. This method utilized differential pressure sensors located at different axial positions in the wellbore to measure the instantaneous pressure drop in the wellbore. These data were used to characterize the axial distribution of cuttings bed in the wellbore and calculate the cuttings bed transport velocity. The impact of fluid density, flow rate, and drill pipe rotation speed on the cuttings bed transport velocity and pressure drop was analyzed. The results indicate that this method effectively describes the characteristics of cuttings bed transport and accurately depicts the axial distribution of cuttings bed within a wellbore. Cutting bed transport velocity is positively correlated with fluid density, flow rate, rotary speed. Increasing the flow rate significantly improves the cuttings bed transport velocity, although a rapid rise in pressure drop limited the maximum flow rate. Increasing the rotary speed can significantly improve the cuttings bed transport velocity and has almost no effect on the wellbore pressure drop. The results provide clarification of the axial transport law of cuttings bed in horizontal wells, providing a theoretical foundation for measuring the axial distribution of downhole cuttings bed and assisting in avoiding the risks of complex wellbore pressure and pipe sticking.