The invention relates to a method for preparing p-type CdS nanowires. The method comprises the following steps of: (1) blending CdS powder and Sn powder in a mass ratio of 2-4:1, adding the mixture on an aluminum oxide boat of a tube furnace and placing a p-type aluminum oxide boat in the downwind direction of the raw materials; (2) continuously vacuumizing to control the pressure in the furnace to be between 200 and 300Torr and introducing argon gas of which the flow rate is 50 to 100sccm at the same time; and (3) controlling the central temperature of a reaction tube to be between 800 and 900 DEG C, and after keeping the temperature for 2 to 4 hours, naturally cooling the product to room temperature to obtain the p-type CdS nanowires. The preparation process of the invention is simple and feasible and can be finished in one step; the repeatability is high; the difficulty of preparing the p-type CdS nanowires is overcome; the stability is high; and the product is expected to greatly promote the development of CdS nanowire-based photoelectric devices, particularly solve the technical problem of wide band-gap II-VI semiconductor material p-type doping.