In order to investigate the role of Map2k1 gene in the gonadal development and sex differentiation of Bellamya purificata， gene cloning， quantitative real-time PCR （qRT-PCR）， in situ hybridization， and RNA interference were employed. The results revealed that the full-length ORF of Map2k1 cDNA was 1 191 bp， encoding 396 amino acids. The MAP2K1 protein contained the S-TKc domain， and its amino acid sequence had high homology with mollusks. Map2k1 was detected in tissues of both sexes， showing the highest expression in the female gonads， where expression significantly differed from that in the male gonads（P<0.01）. In situ hybridization analysis demonstrated strong hybridization signals of Map2k1 in the oocytes and ovarian vesicles of female B. purificata. The RNA interference results showed that in female B. purificata， the interference chain G1 of Map2k1 reached the highest interference rate of 73.1% 12 hours after injection， and led to a significant decrease in the expression of other sex-related genes β-catenin， Cyp17a1， and Sox9. Research had shown that Map2k1 may be involved in the gonadal development and sex differentiation of female B. purificata. This study can provide theoretical reference for the gonadal development and monosex breeding of B. purificata.