Abstract: Based on the scientific observer′s surveys in tropical Eastern Pacific Ocean covering areas 03°S~17°S, 96°W~146°W and 05°N~10°S, 134°W~173°W during July~Nov. 2003 and Feb. ~Nov. 2006 respectively, 202 specimens of crocodile sharks (Pseudocarcharias kamoharai) were collected and analysed. The result showed that the relationship between total length and total weight of crocodile is W=9×10^-5TL^2.3116 for female and W=9×10^-6TL^2.9007 for male. The sex ratio of crocodile shark was nearly 1:1. Female crocodile shark′s total gonad weight was increased with the growth of total length, female crocodile shark adult matured at about 89 cm, males adult about 85~100 cm. The brood of crocodile is 3.85, and size at birth is 40 cm.