The invention relates to a negative oxygen ion generator based on metal micro-needle point discharge and a preparation method thereof. The negative oxygen ion generator comprises a power supply, a cavity provided with an inlet and an outlet, and two metal micro-needles arranged in the cavity. The tips of the two metal micro-needles are oppositely arranged, and the two metal micro-needles are connected with a power supply through wires. Each metal microneedle comprises a base and a microneedle array arranged on the surface of the base. The microneedle array comprises a plurality of rectangular-pyramid-shaped microneedles which are distributed in a matrix mode, wherein each rectangular-pyramid-shaped microneedle comprises a stand column and a needle tip arranged on the stand column. Comparedwith the prior art, the negative oxygen ion generator is a device for generating negative oxygen ions through point discharge of the micro-miniature high-density metal microneedles, and has the advantages of being simple in structure, low in production cost, easy to operate, light, handy, convenient to use and wide in application range and the like.