The invention relates to a pile-base rail plate girder structure and a construction method, and belongs to the technical field of rail and bridge construction. The pile-base rail plate girder structure comprises a pile, a rail plate girder and a cover girder which is horizontally arranged on the top of the pile; the rail plate girder is longitudinally laid; the rail plate girder comprises a pre-stress concrete plate girder; two ends of the pre-stress concrete plate girder are separately supported on one cover girder; the rail plate girder is limited by bosses; and two rail bearing grooves areformed in the top surface of the pre-stress concrete plate girder, and a tooth rail installing structure arranged between the rail bearing grooves is arranged on the top face of the pre-stress concrete plate girder. The method comprises the following steps of construction preparation, rail line pile base perforation, pile assembly, cover girder assembly and rail plate girder assembly. According tothe pile-base rail plate girder structure, a rail function and a bridge function are integrated; the structure is simple; a construction procedure can be simplified; a construction cycle is shortened; construction cost is lowered; the structure is a brand-new railway bridge structure; the construction procedure is simple; construction difficulty is low; construction efficiency is high; and the pile-base rail plate girder structure is applicable to building railway bridges in a slope geographical environment.