Objective To identify the genetic mutation of the gene FOXL2 in a big Chinese family with 4 generations,8 patients and 11 health members which have blepharophimosis-ptosis-epicanthus-inversus syndrome(BPES) type Ⅰassociated with ovarian dysfunction,and demonstrate the correlation between clinical phenotype and genotype.Methods The peripheral blood samples,with 5ml EDTA as decoagulant,from 8 patients and 11 health people in a big Chinese family affected with BPES typeⅠwere collected.The genomic DNA from peripheral blood leukocytes was extracted.7 pairs of primers were designed by the Oligo6 according to the sequence of the FOXL2 gene(GenBank ID AF301906).The exons and the putative core promoter of the FOXL2 gene were amplified using polymerase chain reaction(PCR),and mutation was analyzed by sequencing DNA fragments.Results A novel nonsense mutation at nucleotides in the FOXL2 gene was found in the eight affected patients of the big Chinese family with BPES typeⅠ.No mutation was found in any of the health members in the big Chinese family.Conclusion This is the first reported mutation of the FOXL2 gene in a big Chinese family with BPES typeⅠ.This nonsense mutation in the FOXL2 gene may be an important pathogenesis for the BPES typeⅠin this big Chinese family.It is the first time that a novel nonsense mutation in the FOXL2 gene has ever been found to demonstrate a close correlation between genotype and BPES typeⅠ.