The invention relates to a processing method of cotton and copper alginate blended yarn and belongs to the technical field of yarn manufacturing processes. Copper alginate fiber and cotton are pretreated respectively, and after the copper alginate fiber and the cotton are mixed evenly, mixed fiber is sequentially subjected to opening picking, carding, combing, drawing, roving and spinning, wherein the opening picking process comprises the steps that the mixed fiber sequentially passes through a bale plucker, a mixing opener, a roller card wire opener, a vibration cotton feeding box and a single beater scutcher to be treated, the roller card wire opener and all beater screens of the single beater scutcher are sealed; a half holding and beating gauge is adopted, and in the carding process, controllable half-hold licker-in opening is adopted; needle teeth small in working angle and low in density are adopted in carding machine card clothing. When applied to processing of the copper alginate fiber and cotton mixed yarn, the method has the advantages that the mixed yarn is less in hairiness, high in strength, less in nep, good in yarn levelness and the like.