Objective. To investigate refractive development and prevalence of myopia in children aged 3-6 years in Hebei Province, China, and to explore the developmental law of refraction, so as to clinically guide the prediction and intervention of myopia. Methods. In May 2019, a total of 6120 people were inspected in 68 kindergartens in 11 cities in Hebei Province. Child refractive refraction was checked under noncycloplegia using a handheld binocular vision screener (SW-800, SUOER, Tianjin, China). Axial length (AL) and corneal radius of curvature (CR) were measured using an ocular biometry (IOLMaster 500, Carl Zeiss, Germany). Myopia was defined as spherical equivalent
SE
≤
−
0.75
D
. Results. A total of 5506 children aged 3-6 years met the criteria and were included in the statistical analysis. The prevalence of myopia was 3.49% (1.93% at age 3, 2.90% at age 4, 3.78% at age 5, and 3.88% at age 6). Overall, the mean SE was
+
0.67
±
1.05
D
(
+
0.81
±
1.00
D
at age 3,
+
0.79
±
1.05
D
at age 4,
+
0.67
±
1.08
D
at age 5, and
+
0.13
±
1.01
D
at age 6); the mean CR was
7.76
±
0.26
mm
(
7.78
±
0.26
mm
at age3,
7.75
±
0.25
mm
at age 4,
7.77
±
0.26
mm
at age 5, and
7.76
±
0.25
mm
at age 6); the mean AL was
22.31
±
0.73
mm
(
21.98
±
0.63
mm
at age 3,
22.12
±
0.69
mm
at age 4,
22.34
±
0.73
mm
at age 5, and
22.49
±
0.73
mm
at age 6). Conclusions. Prevalence of myopia increases with age in children aged 3-6 years in Hebei, China. With the increase of age, CR is basically stable, and AL increases gradually. AL/CR, which is closely related to SE, can be used as an indicator to predict myopia and guide clinical work.