The invention discloses a high-fill subgrade filling construction method applicable to red clay regions in mountainous and hilly areas. According to the method, the upper part of the foundation of a high-fill section is mainly composed of cultivated soil, artificial fill and sludge at the bottoms of ditches and ponds, and a lower soil layer is mainly composed of silty clay, red clay, limestone, etc.; an upper soil layer has poor engineering quality and is treated through excavation, replacement and filling; after replacement and filling with plain soil, a ground surface is subjected to impactrolling; after rolling, a test is carried out; if the ground surface is qualified according to test results, site formation is carried out; topsoil on a place to be constructed is removed, a surface loose soil layer is rolled, an access road for mechanical equipment is built, and surface water is eliminated; drainage ditches are dug around a construction area to ensure the smooth drainage of a site; the horizontal elevation of a filling surface is measured, and a horizontal mark is made to control the layer thickness of a fill. The method can reasonably utilize red clay in a local region, lower engineering cost and reduce damage to natural environment.