Abstract: Based on the samples collected by tuna long-line fishery in the tropical waters of the eastern Pacific Ocean (25°S~15°N, 175°E~105°W) during October 2011 to December 2013, we analyzed the stomach content and prey diversity of blue shark (Prionace glauca). The feeding intensity of blue shark was dominated by level one (68%). The composition of feeding intensity between female and male was not significantly different (χ²-test, P>0.1). Teleosts were major prey items (57.3%), followed by cephalopods (97.9% were squid). The diet composition was not significantly different between female and male, but significantly different among individuals. The Shannon-Weiner diversity index (H) and Simpson diversity index (C) for prey items were 1.78 and 0.28, respectively. The index H decreased but index C increased with increasing blue shark size. The prey diversity indices for female blue sharks in maturing, ovulating and gravid stages were slightly different. Cluster analysis shows that the diet compositions of August~October and November~December were more similar than that of January~March.