Brown mud in the golden retriever’s ears may be caused by ear mite infection. At the same time, dogs may also experience ear itching, odor, etc. The dog needs to be treated in time to avoid ear mite aggravation. You can use pet-specific ear cleaning liquid and ear mite spray for dogs, and clean the dog's ear canal once a week; if there are other dogs at home, it is best to isolate and treat them to avoid infecting healthy dogs.