The invention relates to a preparation method of an antibacterial polyvinyl acetal fibre, and the method comprises the following steps of: (1), after uniformly mixing tetrapod-like zinc oxide whiskers and palygorskite fibre, roasting in a vacuum furnace, after cooling, stirring and dispersing sodium hexametaphosphate in absolute ethyl alcohol, then, carrying out atmospheric pressure plasma treatment, ultrasonically dispersing in de-ionized water containing calcium stearate dispersion liquid, taking suspension whiskers in the upper layer of the solution to be filtered, taking a whisker mixed solution, repeating the operation till filtering and purifying, and after filtering and purifying, drying in a vacuum oven, thereby obtaining an antibacterial whisker mixture; (2), taking a titanate coupling agent, diluting and uniformly mixing the titanate coupling agent by using isopropanol, and, after heating, stirring and drying the titanate coupling agent with the antibacterial whisker mixture obtained in the step (1) in a mixing machine; and then, adding a silver antibacterial agent, a silver-loaded zirconium phosphate antibacterial agent, a zeolite antibacterial agent, an EPP (Foamed Polypropylene) bulking agent and calcium stearate, after stirring in the mixing machine, adding a polyvinyl alcohol spinning solution, and stirring at a high speed, thereby obtaining a broad-spectrum antibacterial polyvinyl alcohol spinning solution; and (3), mixing, filtering and defoaming the broad-spectrum antibacterial polyvinyl alcohol spinning solution obtained in the step (2), spinning by using a wet method or a dry method, and carrying out acetalation treatment, thereby obtaining broad-spectrum antibacterial polyvinyl acetal fibre.