Objective: In recent years many papers have emphasized on the relationship between specific language impairment (SLI) and significant weakness in non word repetition task (NRT). The purpose of this study is to examine the effectiveness of NRT training on some related linguistic indicators in children with SLI.

Materials & Methods: In this single subject study with multiple baselines examine the effect of NRT training on some language indicators, in four available children with SLI aged 6/6 to7/6. The language indicators include mean length of utterance (MLU), the percent of content morphemes, inflectional morphemes and grammatical morphemes. In order to determine the effect of NRT training, effect size index was applied.

Results: The effect sizes of MLU in all of them were high. This training also increased the percent of content morphemes in three subjects. Although it had no effect on one of them. Training made grammatical morphemes increase in three subject but it decrease in one them. Finally Three subjects showed decrease on the index of inflectional morphemes and one of them showed increase.

Conclusion: considering effect size, it seems that NRT training improves language indicators in SLI group. As conclusion NRT training would be recommended for SLI group. Key words: specific language impairment/ verbal working memory (phonological loop)/ non word repetition task/ Mean Length of Utterance/ morphology/  teract