Objective To determine the cutoff point of visual acuity to screen refractive error or myopia in children.Methods This was a cross-sectional research.The database of the RESC (Refractive Error Study in Children) were used which were collected from October 2002 to January 2003.The examination included visual acuity measurement (ETDRs visual acuity chart),auto refraction (ARK-30; Nidek Corp.) and ocular health examination.The definition of refractive error was SE≤-0.50 D,SE≥+2.00 D or cylinder power ≤-1.00 D.The sensitivity,specificity,and predictive values were calculated using each patient as a case; a receiver operator curve was plotted.Myopia was defined as:spherical equivalent (SE)≤-0.50 D or SE≤-0.75 D or SE≤-1.00 D.Results The data of 3 715 cases 7-15 years old subjects' were analyzed.A satisfactory sensitivity/specificity profile was obtained which show 0.625 was the cutoff point for refractive error.The sensitivity,specificity,positive and negative predictive values were 71.7％,93.3％,92.9％,72.9％,respectively.And 0.5 was the best cutoff point under three different myopia definitions.The sensitivity for SE≤-0.50 D,-0.75 D or-1.00 D were 66.3％,73.5％,80.7％,respectively.The specificity were 94.3％,94.0％ and 93.5％,respectively.The positive predictive values were 89.7％,88.0％ and 86.3％,and the negative predictive values were 78.9％,85.4％,90.5％.Conclusion 0.625 is advised to screen refractive error,while 0.5 is advised to screen potential myopia subjects who aged 7 to 15.