The regional geological setting, magmatic rock, vent fluid, hydrothermal plume, metalliferous sediment and polymetallic sulfide of the Okinawa trough and the Manus basin in the western Pacific have been studied. The Okinawa Trough has different tectonic and geophysical characteristics from the north to the south with crustal thickness decreases. The southern part of the trough shows variable gravity anomalies and linear magnetic anomalies, while the middle part has the highest heat flow value. The gravity anomalies in the Manus Basin show small variations while the magnetic anomalies show a pronounced E-W trend, and there exist linear magnetic anomalies near the seafloor-spreading center. Oceanic crust has already appeared in the Manus Basin, while the most part of the crust in the Okinawa Trough belongs to transitional crust, and oceanic crust probably appears in some grabens in the middle and southern part. The magma source of basalts from Okinawa trough and Manus basin are both formed by partial melting of mantle source and mixed with subduction composition. Intermediate-acid volcanic rocks with the same magma source of basalt, are products of crystallization differentiation of the basaltic magma. Compared to Manus basin volcanic rocks, volcanic rocks in the Okinawa trough are affected by different degree of crustal contamination. Vent fluid in Okinawa Trough was high temperature (up to 320℃), acid fluid and enriched in metal elements (e.g., Mn, Fe, Zn and Pb). Concentration of Zn2 , Cd2 , Pb2 and Cu2 in hydrothermal plume of Okinawa Trough was significantly higher than that in seawater. The Manus hydrothermal plume showed positive CH4, Mn, Al and δ3He anomalies and a negative pH anomaly. Compared with the vent fluid (220-276°C, pH=2.5-3.5) of PACMANUS hydrothermal field, the vent fluid of DESMOS hydrothermal field was lower temperature (≥88-120℃) and more acid (pH≤2.1). The lower values of δ34SH2S and δD implied the mixing of acid volatile component and magmatic fluid. The distribution and element concentrations of the metalliferous sediments from the Okinawa trough and the Manus basin are different, and the microbial community in the metalliferous sediments from the two areas aslo are different. The hydrothermal products were divided into four types: Zn-rich type, Ba-Pb-Zn type, Si-sulfide type and Si-sulfide-sulfate type in the Okinawa trough and the Manus basin. The Pb and Au concentrations of the polymetallic sulfides in the Manus basin are significantly lower than that in the Okinawa trough.