The purpose of this study was to evaluate effectiveness of Demands and Capacities  Model (DCM) on reducing the severity of preschool children’s stuttering. In a clinical cuasiexperimental design of single group with repeated measurements; 10 preschool stuttered children (5 girls and 5 boys) referred to two speech therapy clinics that were affiliated to Tehran Welfare Organization were selected and were affected by DCM within a period of 12 individual sessions and children’s stuttering  severity was measured according to percentage of syllables stuttered(ss%) at three stages: pretest, mid test and posttest. Obtained data were analyzed according to  analysis of variance with repeated measurements.The results of ANOVA with repeated  measurements showed that DCM has created a statistically significant decrease in preschool children’s stuttering  severity (p <0/01). Result of this study confirmed the effectiveness of DCM in reduction of preschool children’s stuttering severity.