A high aspect ratio in-plane metal microneedle array, a manufacturing method and a clamping and inserting auxiliary device thereof is disclosed. A large-size metal sheet is cut into small metal sheets. A clamping tooling composed of two upper and lower metal cover plates is processed. Inner sides of the upper and the lower cover plates of the tooling are provided with grooves in which the metal sheets are placed and fastened by bolts. Wire cutting is conducted on the tooling and the metal sheets as a whole to obtain a plane metal microneedle array with a plurality of microneedle bodies. In addition, an assembling and clamping device and an inserting auxiliary device of the high aspect ratio in-plane metal microneedle array is provided. The assembled inserting auxiliary device is placed on skin, and the microneedle array is inserted into the skin through the auxiliary device.