【Objective】 To investigate the visual acuity situation and development trend of the preschool children from 4~6 years old and in order to provide the theory basis for the preschool children's vision evaluation. 【Method】 The preschool children from 4~6 years old in the city of Nanjing attended the visual acuity examination and refraction screening in the year of 2011.The results of visual acuity with refraction screening passed were analyzed. 【Results】 The curve of visual development with normal refraction increased as the age increasing.Visual acuity at P₅,P₂₅,P₅₀ was 4.7,4.8,4.9 of 4 years old; 4.8,4.9,4.9 of 5 years old,and 4.8,4.9,5.0 of 6 years old.The rate of visual acuity ≤P₅ was higher in the children with abnormal refraction than the children with normal refraction (P<0.01). 【Conclusions】 The development of visual acuity from 4~6 years old children is continuously prefected as the age increasing.It is important to combine refraction screening and vision monitoring termly and continuously in order to decrease the rate of amblyopia.