Abstract: Through the vertical static loading test of 3-large-diameter borehole cast-in-place piles in muddy rock foundation in Xining city, pile bearing properties, pile axis pressure transmission and pile side and tip resistance are studied, various construction factors such as slurry recycling mode and the continuity of concrete placement that influence the pile engineering properties are analyzed. And some instructive conclusions for design, construction and further study of same piles in same regions are provided.