Objective　To explore clinical and genetic features for a rare genetic disease of hyperprolinemia. Methods　The clinical data of a patient with type I hyperprolinemia admitted were retrospectively analyzed, and related literatures were reviewed. Results　A 7 years and 6 months old boy came to our clinic due to unstable walking with repeated convulsions and abnormal behavior. Blood amino acid and ester acyl carnitine spectrum suggested increased proline level (2951.52 μmol/L), urine organic acid analysis suggested increased 3-hydroxypropionic acid, 3-methyl,crotonyl glycine and crotonyl glycine. Gene sequencing showed two heterozygous mutations in c.1073C>T and c.857C>T in PRODH, which were pathogenic by gene function prediction. Conclusion　For children with unexplained developmental delay seizures and abnormal mental behavior, blood amino acid and urinary organic acid analysis should be performed as early as possible. When blood proline levels are elevated, hyperprolinemia should be highly suspected. Genetic testing should be performed as soon as possible.