Abstract: Screw piles have the advantages of fast installation speed and superior bearing performance, and as the foundation of offshore wind power, they can effectively reduce construction costs and promote the large-scale development of offshore wind power. During the service of wind turbines, screw piles are subjected to huge horizontal loads. However, most of the current research on screw piles focuses on the vertical bearing performance, and it is urgent to study the horizontal bearing performance of screw piles. In this paper, the finite element numerical analysis method is used to analyze and study the influence of blade size and blade position on the horizontal ultimate bearing capacity of a single-blade rigid spiral pile from the perspectives of the rotation center of the screw pile and the influence range of the soil around the pile, and the failure mode of the soil around the pile under horizontal loading is obtained, and the prediction formula of the horizontal ultimate bearing capacity of the single-blade rigid screw pile in clay is proposed. The results show that the horizontal ultimate bearing capacity of the screw pile increases with the increase of the blade diameter, and shows a trend of first increasing and then decreasing and then increasing with the downward movement of the blade position, when the blade is located at the bottom of the screw pile, the horizontal ultimate bearing capacity reaches the peak, and it is recommended to set the blade at 0.3~0.5 times the embedded depth of the pile or the bottom of the screw pile when the screw pile mainly bears horizontal load. When the blade is located above the center of rotation, the soil around the pile presents a "rigid rotational failure accompanied by an inverted wedge". When the blade is located below the center of rotation, the soil around the pile presents a "rigid rotational failure without inverted wedge".