ObjectiveTo explore the effect of Ketogenic diet (KD) in patients with Dravet syndrome (DS).MethodsThe seizures, electroencephalogram (EEG) and cognitive function of 26 DS patients receiving treatment of KD from June 2015 to October 2019 in the Epilepsy Centre of Guangdong 999 Brain Hospital were analyzed retrospectively. Modified Johns Hopkins protocol was used to initiate KD, blood glucose and urinary ketone bodies were monitored in the patients. The effect was evaluated by Engel outcome scale. And the EEG, cognition, language and motor function of the patients were assessed.Results26 DS patients (20 boys, 6 girls) received treatment of KD more than 4 weeks, the seizure of epilepsy were reduced above 50% in 15 patients (57.7%), 2 patients were seizure free. Among them, the effcet of KD can be observed in 7 patients within one week and 3 patients within two weeks, accounting for 66.7% (10/15). 26 cases (100%), 24 cases (92.3%), 20 cases (76.9%), 11 cases (42.3%) were reserved in 4, 12, 24, 28 weeks respectively. 26 patients achieved Engel Ⅰ ,Ⅱ,Ⅲ,Ⅳgrade effect, accounting for 38.5% (10/25), 54.2% (13/23), 65.0% (12/19), 81.8% (9/11) respectively according to Engel scale. The back ground rhythm of EEG showed obvious improvement in 14 patients wthin 16 patients who revieved EEG after KD. 17 patients assessed cognitive, language and motor function after KD, cognitive function was improved in 10 patients, language was enhanced in 11 patients, motor function of 8 patients was enhanced. The main adverse reactions of KD in the treatment process were mainly gastrointestinal symptoms and metabolic disorders.ConclusionKD treatment in DS has many advantages, such as fast acting, being effective in more than half of the DS patients and tolerable adverse reactions. Cognitive, language and motor function were improved in some patients. Drug resistant DS patients are suggested to receive KD treatment early.