The invention belongs to the field of manufacturing of recombined decorative veneers and particularly relates to a manufacturing method of a horizontal ultra-wide multicolored grain recombined decorative veneer. Multiple special procedures such as skip color-change assembling, sawing according to angle, slicing according to angle and special-shaped gluing are arrayed and combined for multiple rounds, and a complete set of processing and manufacturing method is formed. According to the trend and demands of the decorative market, technical parameters such as assembling height, assembling type, sawing angle and sawing thickness are adjusted, and geometric patterns formed by horizontal alternating of grains with different colors and equal widths or unequal widths are manufactured and are different from natural grain patterns such as imitation wood grains. The manufactured horizontal ultra-wide multicolored grains are more complex and variable in color and highlight the characteristics of modern fashion and artificial design. The manufacturing method of the horizontal ultra-wide multicolored grain recombined decorative veneer is simple in manufacturing process and easy to operate, the veneers are glued firmly, the product rate is high, and the product decorative veneer does not easily bend, deform, and generate dry shrinkage and suncrack.