Appropriate infant and young child feeding (IYCF) plays a crucial role in promoting the healthy growth of children. Currently, many Chinese urban parents are seeking care of children from the early childhood education (ECE) institutions, however, little is known about the feeding practices of infants and young children in ECE institutions. This study aims to investigate the complementary feeding practices for Chinese urban children aged 6-23 months in ECE institutions and explore potential factors influencing their feeding practices. This cross-sectional study was conducted among primary caregivers of children aged 6-23 months in ECE institutions across 31 provinces in China from 1 March to 30 April 2023. Convenience sampling was used to recruit caregivers from centres of Gymboree Play & Music (an ECE institution). Self-administered questionnaires were designed using the online survey tool Sojump and distributed through WeChat platform, which collected information on 1) children's complementary feeding practices; 2) food frequency of seven food groups; 3) caregivers' feeding knowledge and practices; 4) frequency of children attended ECE classes and the primary caregivers' daily nurturing care time; 5) source of information on complementary feeding. A total of 2731 children and their caregivers were surveyed, with 416 children aged 6-11 months and 2315 children aged 12-23 months. The prevalence of minimum dietary diversity (MDD), minimum meal frequency (MMF), and minimum acceptable diet (MAD) was 59.4, 60.6, and 39.2%, respectively. Only 17.3% caregivers believed that continued breastfeeding should be at two years or above, and 29.5% children were continuously breastfed at 12-23 months (CBF). The proportion of non-responsive feeding practices among caregivers ranged from 28 to 64%. Except for CBF, the prevalence of other key complementary feeding practices was higher among children who attending ECE classes than those not attending ECE classes (all P < 0.05). Moreover, children aged 12-23 months who received long-nursing care time (≥4h/d) had significantly higher MMF and MAD prevalence than those in short-nursing care time group (MMF = 66.2 vs. 58.8%, P = 0.0003; MAD = 44.2 vs. 38.3%, P = 0.0047). The complementary feeding practices of children aged 6-23 months in ECE institutions in urban China remained suboptimal, and non-responsive feeding practices among caregivers were common. The attendance of ECE classes and the caregivers' daily nurturing care time could be beneficial in ensuring children to comply with complementary feeding recommendations.