The invention relates to a foam coffee alcohol fermentation beverage and a preparation method thereof. Through extraction, dilution or dissolution with hot water, a coffee solution can be made. Distiller's yeast is used as a fermenting agent, and after sealed fermentation, the yeast is removed; and sugar or other food additives are added for allocation, so that the coffee alcohol fermentation beverage rich in foam is made. According to the foam coffee alcohol fermentation beverage and the preparation method thereof disclosed by the invention, a high-concentration caffeine-free coffee solution is used for fermentation, and yeast nutrient substances do not need to be added; post dilution is performed, so that the content of coffee solids in the fermentation solution is reduced, organic acids in the fermentation solution are diluted, the pH value of a mixed solution is increased, and the foam coffee alcohol fermentation beverage is healthier than an ordinary carbonated beverage; a temperature-reduction method and a filtering method are used for stopping fermentation, so that part of sugar in the fermented beverage can be reserved, and the foam coffee alcohol fermentation beverage is more coordinative and natural in taste and rich and prominent in flavor; and CO2 produced during alcohol fermentation and foam promoting substances such as protein, polysaccharide and esters in the coffee mutally react, so that the coffee foams are finer and smoother, and are loose and long-lasting.