Objective：To investigate the effect of 1% cyclopentolate on the power and axis of astigmatism in 5~6 years old preschool children. Methods：From September 2017 to March 2018，a cross-sectional study was carried out in 1 920 children born between September 2011 and August 2012 in Yuhuatai District. The noncycloplegic refractive status inculding spherical power，astigmatic power，and axis angle were measured using an autorefractor Canon RF10. After cycloplegia was indued by 1.0% cyclopentolate，the refractive status was rechecked. The vector method modified by Thibos was used to analysis asitgmatism. Data only from right eye was analyzed. Results：A total of 1 882 children（response rate 98.92%）had complete data from noncycloplegic autorefraction，1 344 children（cycloplegic rate 71.41%）had complete data from cycloplegic autorefraction，so 1 344 children were included in this study. Astigmatism in 5~6 years old children before and after cycloplegia was mainly manifested as with-the-role（WTR），followed by oblique astigmatism，and then against-the-role（ATR）. Spherical equivalent（SE）values in cycloplegic refraction were significantly more hyperopic than those in noncycloplegic refraction by mean difference of（1.48 ± 1.31）diopters（P < 0.001）. The J0 values increased significantly in cycloplegic refraction except the myopic group（P=0.444），while the J45 values had no significant change in any refractive groups（all P < 0.05）. Blande-Altman plots demonstrated the agreement of astigmatism before and after cycloplegia，the 95% confidence interval of the J0 and J45 were -0.24~+0.32 and -0.15~+0.15，respectively. Conclusion：Cycloplegia has a mild effect on astigmatism，especially in the WTR and ATR astigmatisms，but do not reach clinical significant. Non-cycloplegia is still a reliable tool to measure astigmatism for preschool children.