Shell fluxes of solution-resistant planktonic foraminifera, G. scitula and N. dutertrei, collected by moored sediment traps, are examined as a possible tool to reconstruct the surface water convection in the past subtropical western North Pacific. Time-series observation reveals that shell fluxes of these two species fluctuate in an opposite sense. When surface water is warmed and well stratified, N. dutertrei fluxes reach a maximum. In contrast, G. scitula increases in response to the deepening of the mixed-layer. To amplify the response of shell fluxes to climatological variables, the shell flux ratio of G. scitula to N. dutertrei (FG.sci/N.dut) is introduced. The time series FG.sci/N.dut pattern is similar to that of the Monsoon Index (MOI) representing the strength of the East Asian Winter Monsoon. The FG.sci/N.dut is also well correlated with the mixed-layer depth. These correlations allow reconstruction of the ancient MOI and MLD from the faunal ratio.