Objective To analyze the clinical phenotypes and the genetic cause for a child with Williams-Beuren syndrome, and to explore its molecular mechanism. Methods The clinical data and genetic sequencing results of a child with Williams-Beuren syndrome who referred to our hospital with adrenal insufficiency were analyzed. Results The patient, one month and 20 days old boy, visted our clinic because of pigmentation in his whole body. He had a little elve face, pigmentation, which is especially evident in skin crease and his lip, 3 /6 cardiac murmur, umbilical hernia, pigmentation in vulva, and a mass in the left scrotum. The lab examination showed that hyperkalaemia, high level lactic acid, Endocrine hormone displayed a lowlevel cortisol and adrenocor ticotropic hormore was in a high level on feedback. The ultra sound of heart showed supravalvular aortic stenosis, pulmonary artery stenosis and atrial septal defect (II). Perineum Ultrasonography showed bilateral inguinal hernia, and the ultrasound and CT of adrenal gland was normal. Next generation sequencing revealed a 0 . 73 Mb deletion on the 7 q 11 . 23 (chr7 :73 , 442 , 119 - 74 , 175 , 022 ) region of the child. The region included 15 protein-coding genes. Conclusion A child with characteristic manifestation of Williams-Beuren syndrome and adrenal insufficiency was diagnosed using next generation sequencing, and his adrenal insufficiency was rare. The deletion on 7 q 11 . 23 underlied the disease in this boy.