Mucopolysaccharidosis type II is of high genetic heterogeneity. PCR-DNA sequencing was used to study the mutation hot spots in the IDS gene of a Chinese MPS II pedigree. A new mutation (1467-A) not yet reported worldwide was detected. This mutation located at 448th codon in the coding region of exon 9 deletes one "A" at the end of 1467 bp (cDNA). The frame-shift mutation makes the peptide chain shorten from amino acids 550 to 459, probably altering the configuration of IDS enzyme protein remarkably and lowering the activation of IDS greatly. Therefore it is supposed to be the direct cause of the patient with MPS II and to be a necessary premise for prenatal gene diagnosis.