The invention discloses a weaving process of a three-layer forming net. The weaving process specifically comprises the following steps: first bottom layer weaving, surface layer weaving, middle connecting layer weaving, second bottom layer weaving, bottom weft heald lifting, stretching and forming, and cooling and winding. According to the weaving process of the three-layer forming net, 20 heald mesh weaving is adopted, and the surface weft heald lifting step is an even number, so that the formed surface line meshes are straight lines, thereby making the net surface smoother and the quality offinished paper better; 20 heald mesh weaving is used, and 60 steps are one cycle, so that one cycle of a connection line has 12 steps more connection than a weaving method of 16 healds 48 steps, thereby making the net body structure more tight, and enhancing the tensile strength of the net body; and 20 heald mesh weaving is used, and the bottom weft heald lifting step is that two thicker nylon polyester monofilaments are woven side by side, so that the contact area of the bottom surface of the net body to a paper machine is increased, the wear resistance of the net body is improved, and the retention rate of the prepared three-layer forming net is improved by 13%.