The invention relates to a production method of tight sirospun yarn of combed crystal cotton. The production method comprises the following sequential working procedures: combed cotton preparation; opening, cleaning and blending of combed cotton and crystal cotton; cotton combing; drawing; roving; mixing of sirospun yarn of nylon filament; and winding. According to the invention, crystal cotton fiber is blended with the combed cotton fiber, the tight sirospun yarn of the nylon filament is added during the spinning working procedure, and a double-rough-yarn feeding device and a tight spinning device are additionally installed on a traditional ring spinning frame, so that two threads of rough yarn are simultaneously fed to a drafting region, a certain spacing is reserved between drafted fiber strands, and the drafted fiber strands are gathered, converged and twisted at the downstream of the roller chop to obtain yarn. Under the action that the fiber strand twisting triangular region is canceled due to bundling action and two threads of fiber strands are combined, the filoplume value of single yarn is obviously reduced, the yarn evenness is significantly improved, the fracture strength is greatly increased and better resultant yarn quality is obtained; and functional yarn with high strength, high hygroscopicity, cleanness, high elasticity and bacteriostatic characteristic is produced by the equipment.