Objective: The present study evaluated the quality of individual items and obtained preliminary evidence on the reliability and validity of a spatial ability assessment tool for children aged 5–6 years. Methods: Liu’s (2021) assessment tool served as the basis for the assessment. The participants were 112 children from four classes in one kindergarten. The 15 dichotomously scored items were grouped into spatial perception, mental rotation, and spatial visualization. Item characteristics, internal consistency, preliminary structural evidence, and associations between age and spatial ability were examined. Results: The items varied considerably in difficulty and discriminatory performance. Item 5 was answered correctly by 92.9% of the children and showed a relatively weak corrected item–total correlation, suggesting that its difficulty may need adjustment. Items 6 and 7 were difficult, but both retained some discriminatory capacity, so their low accuracy alone does not warrant deletion. KR-20 coefficients were 0.713 for spatial perception, 0.293 for mental rotation, 0.778 for spatial visualization, and 0.657 for the full assessment. For children aged 61–75 months, age was not significantly related to any dimension or to the total score. Conclusion: The assessment provided preliminary evidence of acceptable item performance and reliability for several components of spatial ability in 5- to 6-year-old children. However, the mental rotation dimension showed limited internal consistency, and Item 5 may require further revision. Further studies with larger and more diverse samples are needed to examine the stability of the proposed structure and to strengthen the validity evidence for the assessment.