Recent studies have emphasized the important role of moisture in altering tropical cyclone (TC) vortex structure. Latent heat released in outer rainbands induces change in the secondary circulation, and exerts negative impact on TC inner core intensity. This study is to further explore the TC structural behavior with the presence of vertical wind shear. Typhoon Talim (2005) was simulated using the Weather Research and Forecasting (WRF) model, and sensitivity experiments were conducted by artificially modifying the amount and distribution of moisture around TC vortex. With the presence of an easterly vertical wind shear, the simulated Typhoon Talim developed quasi-stationary outer rainbands that concentrate in the southwestern (downshear left) sector. Air from the north (upstream side of the outer rainbands) traveled faster into TC core than air from the other directions, thus Typhoon Talim was more sensitive to moisture variations in the north than in the south. With enhanced moisture supply into outer rainbands, simulated TCs grow larger in size. However, their inner core intensity and strength are weakened because latent heat released in outer rainbands induces updrafts and reduces mid- to low-level radial inflow that advects absolute angular momentum into inner core. On the contrary, TCs simulated with reduced moisture supply become smaller in size since drier environment inhibits convection in outer core region. The relatively convection-free outer core region favors the formation of strong radial inflow that accelerates the inner core spin-up process. This causes TCs to contract while their inner core strength and intensity increase. Although moisture in outer core region imposes a negative effect on inner core intensification, it contributes to the maintenance of outer core strength and TC size by inducing more convection in the outer core region. Thus, abundant moisture supply in TC outer core region is critical to the growth of horizontal extent of TC primary circulation.