Abstract: Based on the data by scientific observer survey in the tropical Central and Eastern Pacific Ocean(05°N-10°S,134° W-173°W) by the tuna longline fishery targeting bigeye tuna during Feb.-Nov., 2006, with the total 223 sets, 22 sea turtle bycatch were observed and analysed. The incidental sea turtles were classified as 5 species, namely green sea turtles (Chelonia mydas),loggerhead (Caretta caretta),oliver ridley turtle (Lepidochelys olivacea), hawksbill turtle (Eretmochelys imbricata) and leatherback turtle (Dermochelys coriacea) with total 22 individuals.There were 13 sea turtles mortality after capture. The incidental catch rate is 0.09865 per set and 0.374 0 per thousand hooks. The interaction between fishing gear and sea turtles showed that sea turtle body were hooked with mouth accounting for 41.0%, external parts 13.6%, swallowed 13.6%，foreleg 18.2% and mainline entangement 13.6%. Most sea turtle bycatch occurred north of 04°S and almost all the year round. Analysis was also made to identify the specific hook number for interaction with sea turtles. Discussion was made on factors for affecting catch rate and mortality. Measures were suggested on conservation and by-catch mitigation for sea turtles.