The pearl oyster Pinctada fucata martensii is an economically valuable shellfish that is cultured for seawater pearl pro-duction, which mainly depends on oyster growth. However, the growth mechanisms of the pearl oyster are still poorly understood. In this study, oysters were grouped with relative growth rate, including fast-growing (FG) group and slow-growing (SG) group. Oxford Nanopore Technologies (ONT) long-read sequencing was applied to investigate the molecular mechanisms involved in the growth of this species. Five alternative splicing (AS) types were analyzed in both FG and SG groups, which include alternative 3\' splice site, alternative 5\' splice site, exon skipping, intron retention, and mutually exclusive exon. Transcriptome analysis showed that four of five different AS events (excluding mutually exclusive exons) occurred more frequently in FG than in SG oysters, and the five main AS types exhibited different characteristics. The AS events that were detected may be involved in growth, and the difference in ex-pression of AS events between FG and SG oysters may be involved in the mechanism underlying the difference in growth. Fifty dif-ferentially expressed genes (DEGs) were identified between the FG and SG oysters. The results showed that 40 genes were signifi-cantly up-regulated in FG oysters, while 10 genes were significantly down-regulated in SG oyster. Several genes related to nutrient metabolism, shell formation, and immunity were more highly expressed in FG oysters than in SG oysters. In summary, FG oysters exhibited higher metabolic and biomineralization activities and had a more powerful immune system than SG oysters. These results provide insight into the growth of P. f. martensii that can be used to improve breeding programs.