The aim of this study is to examine the association between insufficient sleep and astigmatism, as well as its related refractive components, in preschool children. Preschool children aged 3 to 6 from two kindergartens in Shanghai participated in this study. Non-cycloplegic refraction was assessed using an auto-refractor (Topcon KR-800, Tokyo, Japan), and biometric parameters were measured with the IOL Master 700 (Carl Zeiss, Jena, Germany). Sleep duration and lifestyle information were collected via questionnaires. Total Astigmatism (TA), Anterior Corneal Astigmatism (ACA), Internal Astigmatism (IA), and Compensation Factor (CF) were calculated from vector components J