Objective To investigate the distribution of refractive state in 3- to 6-year-old children with subnormal vision,and to analyze the relationship between different refractive types and amblyopia. Methods A descriptive study method was adopted to select 1 644 3- to 6-year-old children (3 288 eyes) with subnormal vision. Refraction and corrected visual acuity were detected after cycloplegia using 1% atropine ointment. The distribution of refractive state,the incidence rate of anisometropia,astigmatism and amblyopia at different age stages were studied. Results The majority of the children were hyperopia. The first refractive causes of amblyopia were compound hyperopic astigmatism (60. 04%). With the increase of age,the proportion of children with hyperopia decreased gradually while myopia increased. The rate of anisometropia was 14. 05%,significantly decreased with increased age (χ²=37. 31,P＜0. 01). There was a significant decrease in anisometropia with increased anisometropia (χ²=79. 181,P＜0. 01). Difference was statistically significant on astigmatism diopter and astigmatism axis in different age groups (χ²=95. 919,150. 79, P＜0. 01). The rate of amblyopia was 12. 77%. The incidence of amblyopia was higher when the spherical equivalent difference between the two eyes was not less than 1 diopter. There was a significant increase in the occurrence of amblyopia with increased anisometropia (χ²=379. 15,P＜0. 01). Conclusions The majority of 3- to 6-year-old children with subnormal vision have hyperopia. Hyperopia,astigmatism,and anisometropia are prone to cause amblyopia.