Objective: To investigate the impact of preschool children s aquatic motor skill (AMS) acquisition on their fundamental motor skill (FMS) development and the correlation between AMS and FMS development, so ao to provide a scientific basis for early childhood education and physical education teaching. Methods: From April to June 2024, 60 children, recruited by random sampling from a kindergarten in Taiyuan, were stratified randomly divided into an experimental group ( n =30) and a control group ( n =30). The experimental group were further divided into five classes of six each. They received AMS practice interventions twice weekly, 40 minutes per session, over eight weeks (16 sessions total) at a designated swimming center. The control group maintained their usual routine. Children s FMS and AMS were assessed pre and post intervention using the Test of Gross Motor Development-3rd (TGMD3) and Actual Aquatic Skills Test (AAST), respectively. Before and after test comparisons within and between groups employed t-tests, Wilcoxon signedrank tests, ANCOVA (including ranktransformed ANCOVA), and Cohen s d effect sizes were calculated for standardized mean differences. Spearman rank correlation was used to analyze relationships between FMS and AMS. Results: After the aquatic learning, the experimental group scored significantly higher than the control group on locomotor skills ( F=20.47, P <0.01, η 2=0.26), FMS ( F=4.59, P =0.04, η 2=0.08), and AMS ( F=109.71, P<0.01, η 2=0.79). The experimental groups improvement in locomotor skills 5.0(3.8, 7.3) versus the control group (2.8±2.5) yielded a medium effect size (Cohen s d =0.71); AMS gains in the experimental group [26.0(20.8, 28.0)] versus controls [1.0(0, 2.3)] showed a very large effect size (Cohen s d =4.73) (both P <0.01). Among preschool children, AMS acquisition was positively correlated with locomotor skills ( r =0.39) and overall FMS ( r =0.43)(both P <0.05). Skill specific assessments revealed lower proficiency in headfirst entry (immersion), treading water, and sagittalplane rotation. Conclusion Preschool children s acquisition of AMS has a positive effect on their FMS, with mutual facilitation between the two, especially in locomotor abilities.