Background: Deficit in motor performance is common in children with intellectual disabilities (ID). A motor function measure with sound psychometric properties is indispensable for clinical and research use. The purpose of this study was to compare the psychometric properties of three commonly used clinical measures for assessing motor function in preschoolers with ID: the Bruininks-Oseretsky Test of Motor Proficiency-Second Edition, the Movement Assessment Battery for Children-Second Edition and the Peabody Developmental Motor Scale-Second Edition (PDMS-2). Method: One hundred and ninety-one children aged 3-6 years with ID were evaluated with the three measures at three time points: two baseline measurements with a 1-week interval before the intervention, and a follow-up measurement after 6 months of paediatric rehabilitation programme. One hundred and forty-one participants completed all of the assessments. The distribution (ceiling and floor effects) and reliability (internal consistency and test-retest reliability) of each measure were examined. Concurrent validity, predictive validity, and responsiveness were examined as well. Results: All measures, except for the PDMS-2, had significant floor effects or ceiling effects at one or more time points. The three measures had good internal consistency (Cronbach alpha greater than or equal to 0.86) and test-retest reliability (intraclass correlation coefficient greater than or equal to 0.96). The Spearman rho correlation coefficient for each pair of the three measures was greater than or equal to 0.80, indicating high concurrent validity. The predictive validity of the three measures was satisfactory (Spearman rho greater than or equal to 0.52). The responsiveness of the three measures was moderate (0.47 less than or equal to effect size less than or equal to 0.74). The minimal detectable changes of the three measures were satisfactory. Conclusions All three measures showed sufficient reliability, validity responsiveness in preschoolers with ID, but the PDMS-2 is recommended for its superior psychometric properties