The invention discloses a combined foundation capable of bearing a horizontal load and a method. Through the combined foundation, the problem that horizontal load bearing capacity is insufficient in an engineering foundation is solved, anchor rods, piles and an underground continuous wall are combined together to serve as a foundation for bearing the horizontal load, the advantage that the underground continuous wall is high in horizontal stiffness is achieved, the horizontal bearing capacity of a component at a passive zone position is improved through the characteristic that the contact area between the continuous wall and soil is large, meanwhile, the horizontal bearing capacity of active zone soil is achieved by arranging the horizontal anchor rods at an active zone position, and firm embedment of the foundation is ensured through the lower piles. According to the technical scheme, the combined foundation comprises the underground continuous wall, the four edge corners of the bottom of the underground continuous wall are arranged on the horizontal load-bearing piles, the load-bearing face of the underground continuous wall is provided with the multiple rows and columns of horizontal anchor rods, and the top of the underground continuous wall is provided with a top plate.