Background <p>Spastic cerebral palsy (CP) is a common cause of motor disability in children which caused by non-progressive brain injury. This study aimed to investigate the correlation between quantitative brain MRI parameters and motor dysfunction in children with spastic CP.</p> Methods <p>91 children with spastic CP and 91 controls were recruited. Brain volumes were measured using high-resolution T1-weighted Magnetic resonance imaging (MRI). Gross motor function was assessed using Gross Motor Function Measure-66 score (GMFM-66) and the muscle tone was evaluated by modified Ashworth scale and scored by modified Ashworth scale score.</p> Results <p>Children with spastic CP showed significantly reduced total brain volume, white matter volume, gray matter volume, and white matter/total brain volume ratio compared to controls. In children with spastic CP, white matter volume and white matter/total brain volume ratio positively correlated with GMFM-66 scores (<i>r</i> = 0.56, <i>p</i> &lt; 0.001; <i>r</i> = 0.47, <i>p</i> &lt; 0.001). The muscle tone of specific muscles negatively correlated with brain volumes.</p> Conclusions <p>White matter volumes are closely related to motor dysfunction in children with spastic CP. Quantitative MRI may serve as objective biomarkers for evaluating the severity and prognosis of spastic CP, providing basis for individualized rehabilitation strategies.</p>