The invention provides a passion fruit dietary fiber beverage and a preparation method thereof, and belongs to the field of food processing. The passion fruit dietary fiber beverage which is obtained by taking all passion fruits as raw materials through the combination of treating processes of cutting of fruit husks into sections, acid protease treatment on pulp, ethanol soaking and filtering treatment on fruit seeds as well as subsequent fermentation and homogenizer treatment can more completely keep nutritional ingredients. The obtained passion fruit dietary fiber beverage is convenient to eat and good in taste, has high soluble dietary fiber content, has rich nutritional values and good health-care effects, and is suitable for all people to eat.