The invention relates to a big diameter steel pipe protective wall artificial digging-hole bottom expanding pile and a building foundation reinforcement method. The invention aims to provide a big diameter steel pipe protective wall artificial digging-hole pile structure, which can solve the problems of common pile foundations in the prior art, effectively improves uplift bearing capacity of single piles, has the advantages of convenient construction and excellent economy, and is reliable in pile quality, high in bearing force of the single piles and rapid in construction speed. A big diameter steel pipe protective wall artificial digging-hole pile comprises a big diameter steel pipe pile which is pressed into design depth through static pressure of an anchor rod, wherein the big diameter steel pipe pile is connected trough a plurality of joints, steel pipes are sleeved outside connecting positions of two adjacent joints, expanding holes are formed on the pile ends of the steel pipe piles, steel reinforcement cages are arranged in the steel pipe piles, parts of steel reinforcements which are arranged on the expanding holes in the steel reinforcement cages outwardly expand, and expanding heads are formed on the expanding holes by casting concrete. The big diameter steel pipe protective wall artificial digging-hole bottom expanding pile and the building foundation reinforcement method effectively improve bearing force of pile foundations.