Background Childhood vision loss represents a significant public health burden worldwide, with the majority of these cases being treatable or preventable if identified early. This study aimed to investigate the contemporary prevalence, causes and refractive error-related risk factors of visual impairment among preschool children in Beijing, China. Methods In this cross-sectional study, preschool children aged 36 to 83 months were enrolled to undergo comprehensive ocular examinations, including visual acuity, autorefraction before and after cycloplegia (1% cyclopentolate), ocular biometry, anterior segment examination, and cover and uncover test. Visual impairment (VI) was classified according to the Pediatric Eye Evaluations Preferred Practice Pattern guidelines, which define it as presenting visual acuity (PVA) in either eye exceeding 0.4, 0.3, and 0.2 logMAR for respective age groups of 36-47, 48-59, and 60-83 months, and an interocular difference (IOD) of two or more lines in PVA. Results This study included 1,473 children with an average age of 4.89 +/- 0.76 years; 52.5% were boys. The mean PVA for the worse-seeing eyes across the age groups 36-47, 48-59, 60-71, and 72-83 months were 0.29 +/- 0.11, 0.22 +/- 0.11, 0.18 +/- 0.11, and 0.14 +/- 0.11, respectively (ANOVA; P < 0.01). For the better-seeing eyes, the mean PVA were 0.24 +/- 0.10, 0.17 +/- 0.09, 0.13 +/- 0.09, and 0.09 +/- 0.10 (ANOVA; P < 0.01). The overall prevalence of VI was 17.99% in worse-seeing eyes, 8.83% in better-seeing eyes, and 1.77% for IOD. No significant differences were observed between boys and girls in mean PVA and the prevalence of VI. The primary causes of VI were refractive errors, including astigmatism (24.2%), hyperopia (19.6%), myopia (9.1%), and anisometropia (6.4%), followed by amblyopia (9.8%) and strabismus (2.3%). Factors associated with VI, as determined through both univariate and multivariate analyses, included older age (OR = 1.472, P < 0.01), greater absolute value of cylinder (OR = 5.691, P < 0.01), myopia (OR = 85.432, P < 0.01), and anisometropia (OR = 3.805, P = 0.02). Conclusions This extensive study provides contemporary insights into the prevalence and causes of VI in preschool children in Beijing, China. The findings reveal a higher prevalence of VI compared to previous reports from Western countries, highlighting the critical need for ocular screening in preschool children and support from local governments to promote early prevention strategies against refractive errors.