Objective - To evaluate the quantitative diffusion value in ipsilateral cerebral peduncle of patients with differing motor function abilities and analyse the thresholds discriminating the poor motor function disability. Method - Twenty-nine patients who previously suffered stroke underwent diffusion tensor imaging examinations. Motor function was evaluated 8 months after the event. The ipsilateral apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of cerebral peduncle and ADC ratio and FA ratio of patients with different motor function scales were analysed. Results - The ipsilateral FA value and FA ratio were distinctly different in patients with different motor function scales, and significantly correlated with the motor function scales. There was no significant difference of ipsilateral ADC and ADC ratio, and neither had correlation with motor function scale. The patients with poor motor function scale could be discriminated by the cutoff value of ipsilateral FA of 0.453 and FA ratio of 0.623 with sensitivity of 90%, 75% and specificity of 88.9%, 88.9% respectively. Conclusions - The ipsilateral FA value and FA ratio were feasible and better imaging indices in discriminating patients with poor motor function ability.