The 85 strains of Vibrio parahaemolyticus harboring the Vibrio parahaemolyticus type Ⅵ secretory system (T6SS) related genes were investigated in this study. The T6SS1⁺ and T6SS1^- strains chosen were analysed in mixed culture to explore their intraspecific competition. The qPCR technology was employed to analyze the expression of related genes of T6SS. The results show that:although all Vibrio parahaemolyticus harbored T6SS2, T6SS1 were found in a certain number of strains, 85 strains of Vibrio parahaemolyticus all carried T6SS2, and 62 strains of Vibrio parahaemolyticus carried T6SS1, of which 41 were clinical isolates, accounting for 93.2% of all clinical isolates; there were 21 environmental isolates, accounting for 51.2% of all environmental isolates, T6SS1 gene clusters were different in Vibrio parahaemolyticus from different sources. Some T6SS1⁺ strains had significant intraspecific competitive advantages, which could suppress the growth of other strains in mixed culture. Compared with monoculture strains, the expression levels of T6SS1 and T6SS2 strains were significantly up-regulated in mixed culture. The reason for this phenomenon might be that strains could strengthen the expression of its related T6SS1 and T6SS2 genes to enhance its competitiveness in the species. The influence of Vibrio parahaemolyticus type Ⅵ secretion system on its intraspecies competition was preliminarily explored, providing scientific reference for further revealing Vibrio parahaemolyticus T6SS function.