The invention provides a method for preparing beer by using pomelo. It comprises following steps: washing pomelo, removing epiderm (or not) and bad part, separating pulp from peel, cleaning peel, cutting peel, adding water and grinding, controlling temperature, adding proper amount of acid and stirring evenly, adding enzyme and getting peel enzyme reaction liquid, beating pulp, removing seed and getting pulp slurry, adding proper amount of acid and stirring, adding enzyme and getting pulp enzyme reaction liquid; mixing peel enzyme reaction liquid with pulp enzyme reaction liquid according to a certain proportion, stirring evenly and getting pulp slurry enzyme reaction liquid, filtering and getting pomelo clear juice; mixing filtered pomelo clear juice with brewed beer, loading, sealing, disinfecting, cooling, packing and getting pomelo beer; or mixing pomelo enzyme reaction liquid with prepared cereal mash, boiling, cooling, injecting yeast and preparing with beer processing steps and getting fermented pomelo beer.