Abstract: The author reported a case of sebaceous dysplasia, which was treated by radiotherapy with ⁹⁰Sr applicator. Sebaceous dysplasia is caused by physiological variation and dysplasia of sebaceous glands. This case presents as a miliary, pale white, papular lesion in the upper lip. ⁹⁰Sr applicator has the advantages of painless, simple operation, obvious curative effect, mild adverse reaction and no obvious sequelae in the treatment of sebaceous dysplasia.