Objective To evaluate the effect of dental water jet on oral hygiene maintenance in orthodontic patients with fixed appliances. Methods One hundred and twenty orthodontic patients with fixed appliances were randomly assigned into the manual toothbrush group and the dental water jet group. Dental plaque was evaluated and compared before the bonding of orthodontic appliances, three months and six months after the treatment. Results There was no significant difference between two groups before treatment. But the dental water jet group was superior than the manual toothbrush group in dental plaque index 3 and 6 months after treatment. Conclusions Dental water jet can reduce dental plaque and im -prove the oral hygiene of patients with fixed appliances.