Whenever a patient comes to the male infertility clinic, the doctor will always ask him if he has had mumps, and they always wonder if mumps has anything to do with infertility. Mumps is a common respiratory infectious disease in preschool and school-age children. The pathogen is mumps virus, which is transmitted through salivary droplets. It starts with a cold-like illness, followed by parotid enlargement and localized pain, which usually resolves in 1-2 weeks. However, it is sometimes combined with orchitis, which is characterized by swelling, pain or drooping of the testicles, accompanied by systemic symptoms such as fever, chills, nausea, vomiting, and severe atrophy of the testicular tissue. It is generally believed that mumps combined with orchitis before puberty is rare, even if the involvement can usually be completely recovered, so the chances of causing permanent damage to the testicles are less; but after puberty mumps is easy to be complicated by orchitis, when the mumps virus invades the testicular tissues, the sperm-producing varicocele in the testes is destroyed, resulting in permanent damage to the testes and causing infertility. Combined orchitis accounts for 1/5 to 1/3 of mumps patients, and 2/3 of them have unilateral disease, but this does not mean that the opposite testis is not involved, and degenerative lesions can still be seen in both testes. Degenerative lesions can still be seen in both testes. Bilateral testicular involvement can lead to lifelong infertility and is difficult to cure. Therefore, bed rest and active treatment must be taken care of after this stage of mumps to avoid testicular inflammation or to reduce the extent of testicular inflammation.