Objective: The aim of this study is provide a test to examine the effect of word length on spelling errors and determination of its validity and reliability.

Materials & Methods: This study is a descriptive and validity assessment research. The samples selected by non probability sampling from the 8th territory of ministry of education (one class from girlish school and one class from boyish school). At the first, the words of Farsi book were analyzed based on word length (the number of syllables), then 241 out of 494 words were selected. They included every syllabic structure such as 1-5 syllabic words. Different experts like speech and language pathologist, linguists and teachers scored those words. Finally 40 words selected as words of test and dictated to students at first grade by 2 testers during 2 stages separately. Errors were determined and analyzed by using pearsonian correlation coefficient and paired T – test. 

Results: The findings show the coefficient correlation between different performances is high. In boys there is no difference between mean of the number errors in different performances (the amounts of P are P= 0/33 & P=0/56 in 2 administrations by two testers) but in girls there is (the amounts of P are P=0/002&P=1 in 2 administrations by two testers). It can be because of difference between boys and girls in spelling or condition of test.

Conclusion: These findings show this test have high validity and reliability.