The present research has aimed to compare efficacy of cognitive-behavioral and metacognitive approaches on thought fusions and washing-cleaning obsessions in patient with obsessive-compulsive disorder. The study utilized quasi-experimental design with pretest - posttest model has two experimental groups. The population included all of the girl students at the university of science and technology of Iran in 2014-2015.initial sampling by the recall of implementing the study was conducted voluntary and all the voluntaries completed Padua inventory and among them 12 people who suffered from obsessive-compulsive disorder and verified by clinical psychologist ( base on DSM5) were selected by available sampling and randomly divided into two groups of cognitive-behavioral (n=6) and metacognitive (n=6) groups. Then all patient filled Thought Fusion Instrument and cognitive-behavioral and metacognitive interventions was applied. each of interventions was performed in 10 sessions (2 hours per sessions).in order to analyze mixed multi factorial ANOVA and repeated measure one way ANOVA methods has been used. Both metacognitive therapy (p < 0.001) and cognitive-behavioral therapy (p < 0.001) were effective in reducing thought fusion at the end of treatment and after a one-month follow-up < span dir="RTL" lang="FA">. In addition, Both metacognitive therapy (p < 0.001) and cognitive-behavioral therapy (P=0.001) were effective in reducing obsessive-compulsive disorder. Also, There was no significant difference between the effectiveness of cognitive-behavioral and metacognitive approaches on thought fusion (P=0.07), at the end of treatment and after one month follow-up. So metacognitive therapy as new therapeutic areas to the extent of psychology, is effective as much as cognitive-behavioral therapy in reducing thought fusion and symptoms of obsessive-compulsive disorder and it’s subscales, and can be used as an alternative treatment.