It is normal for dogs to vomit yellow foam and defecate, which may be caused by eating too much, eating too fast, indigestion, gastrointestinal diseases, food deterioration, etc. If the dog is in good mental state and has no other abnormalities, You can first deprive the dog of food and water, and then feed it some probiotics; if the dog appears to be in low spirits, does not eat or drink, and frequently vomits, it is best to take the dog to a pet hospital for examination and treatment.