The invention discloses a double concave trapezoidal drill. A front concave trapezoidal tool post I, a rear concave trapezoidal tool post I, a front concave trapezoidal tool post II, a rear concave trapezoidal tool post II, a front convex trapezoidal tool post and a rear convex trapezoidal tool post cut a soil body at the lower end during rotation; the front concave trapezoidal tool post I and the rear concave trapezoidal tool post I cut the left end of the soil body into a double concave trapezoidal end during rotation; the front concave trapezoidal tool post II and the rear concave trapezoidal tool post II cut the right end of the soil body into a double concave trapezoidal end during rotation; the cut soil body is mixed in slurry; high-pressure water is continuously injected; slurry flows out from a hole continuously; a hole with double concave trapezoidal ends at the left and right ends is formed during downward pressing of a drill pipe; concrete is poured into the hole, so that a concrete concave trapezoidal pile is formed.