Objective:To report a genetically proven Kennedy disease pedigree in China and to discuss its clinical presentations,pathological features and molecular mechanism,so as to provide more information on Kennedy disease.Methods: We conducted a complete survey of the family,including 3 generations and 41 individuals. The proband was given a thorough clinical examination including CK level,EMG,testosterone level,nerve biopsy,and muscle biopsy.Genomic DNA was extracted from the peripheral blood; the repeats of CAG in the exon 1 of androgen receptor was amplified by PCR and sequenced directly.Results: The sequencing result showed that the proband（Ⅲ-11) had a CAG repeat of 54）; one patient (Ⅳ-2) had a CAG repeat of 55; one had a CAG repeat of 54; one presymptomatic individual had a CAG repeat of 54（Ⅳ-8）. There were 3 female carriers（Ⅱ-6,Ⅲ-3,and Ⅲ-15）.The CPK and testosterone levels were increased in the proband.EMG revealed neurogenic injury.Nerve biopsy revealed demylination change in the peripheral nerve and muscle biopsy revealed muscle atrophy originated from nerve.Conclusion: Kennedy has no characteristic clinical symptoms,and gene diagnosis is the gold standard.The progression of SBMA is usually much slower compared with those of bulbar atrophy and atrophic lateral sclerosis(ALS).