The invention discloses a preparation method of an annular cavity surface-equipped and difference frequency terahertz-emitting quantum cascading laser structure. The preparation method comprises the following steps of 1, enabling a lower waveguide layer, a lower optical limiting layer, a first active layer, an interval layer, a second active layer, an upper optical limiting layer and an upper waveguide layer to be grown on a substrate in sequence; 2, removing the upper waveguide layer, etching multiple gratings in the upper optical limiting layer in a radial pattern to form a dual-cycle annular grating; 3, performing re-growth of the upper waveguide layer on the etched upper optical limiting layer; 4, etching an annular ridge structure in the upper waveguide layer downwards, wherein the etching depth reaches the lower optical limiting layer; 5, filling the trenches of the etched annular ridge structure with semi-insulated InP: Fe; 6, performing evaporation of a front surface metal electrode on the annular ridge structure, the trenches of which are filled with the semi-insulated InP: Fe, and then performing gold plating; 7, performing thinning and polishing on the substrate, and performing evaporation of a back surface metal electrode on the back surface of the substrate; and 8, etching the metal electrodes to prepare two-stage annular surface metal gratings to complete preparation.