The invention discloses a multilayer testing sampling valve. The multilayer testing sampling valve comprises a mandrel and a shell; the shell is shaped like a cylinder, a channel with a flared section is formed in the lower section of an inner cavity of the shell, a through hole matched with the outer diameter of the mandrel is formed in the top end of the shell, the mandrel with a main liquid channel penetrates through the through hole, two o-shaped sealing rings are embedded in the inner wall of the through hole, the sealing effect is achieved when the mandrel moves up and down in the through hole, a convex ring matched with the inner cavity of the shell is formed on the outer wall, on the lower half part, of the mandrel, two o-shaped sealing rings are embedded in the outer peripheral face of the convex ring, the mandrel, the convex ring and the inner cavity of the shell can form a closed sampling cavity, a mandrel side opening is formed in the side face of the upper portion of the mandrel, when the bottom of the convex ring is located at the bottom of the inner cavity above the flared section, the mandrel side opening is just located between the o-shaped sealing rings of the through hole in the top end of the shell, and the sampling cavity is a closed cavity. According to the multilayer testing sampling valve, switching-on and switching-off are only for a single layer and do not affect communication of a main runner.