The invention relates to a process for manufacturing a preimpregnated fibrous material containing a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein the preimpregnated fibrous material is produced as a single unidirectional tape or of a plurality of parallel unidirectional tapes and wherein the process includes a step of impregnating, in particular fully and homogeneously, the fibrous material that is in the form of a roving or of several parallel rovings with the at least one thermoplastic polymer matrix that is in powder form, the impregnating step being carried out by a dry route in a tank and the control of the amount of the at least one thermoplastic polymer matrix in said fibrous material being achieved by control of the residence time of said fibrous material in the powder, with the exclusion of any electrostatic process with intentional charging.