Generalized anxiety disorder (GAD) according to a chronic course, high prevalence and comorbidity with other psychological disorders, as one of the most debilitating disorders is adult, so addressing effective treatment methods and more economically for this disorder is beneficial and necessary. The aim of the present study was to compare the efficacy of intolerance uncertainty therapy (IUT), Buspirone and the combination of IUT with Buspirone in improving symptom of patients with (GAD). In a clinical trial of quasi-experimental research with pretest-posttest of the patients admitted to psychiatric and psychological clinics and centers in Tehran 24 patients were selected with GAD and randomly assigned to three groups to IUT, Buspirone (5-60 mg per day) and combination. Data before and after the intervention were collected by generalized anxiety disorder scale (GADS-7), intolerance of uncertainty scale (IUS), Penn State Worry Questionnaire (PSWQ), Beck Depression Inventory-II (BDI-II) and Work and Social Adjustment Scale (WSAS). The data were analyzed using a Kruskal Wallis test, Mann-Whitney U-test, and one-way Analysis of Covariance. The results of this study showed Both treatments IUT and combined treatment in comparison with Buspirone led to significant improvements in alleviating the symptoms of generalized anxiety disorder, intolerance of uncertainty, worry, depression and work and social adjustment (p<0.01). Also, the result of Mann-Whitney U-test and one-way analysis of covariance showed there were no significant difference between IUT and combined treatment. IUT and combination therapy are more effective than Buspirone (5-60 mg per day) in improving of GAD are. However, it seems adding medication (Buspirone) to IUT does not improve the patients with GAD.