Semiconductors typically exhibit long-wavelength LSPR absorption in the infrared region due to lower carrier density. Tuning the carrier density of semiconductors and blue-shifting their LSPR absorption to the visible and near-infrared region has always been a great challenge. Herein, we discussed how the controllable carrier of (Ag)_x(MoO₃)_y composite influences the LSPR based on SERS test and UV–Vis–NIR absorption spectra. We were surprised to find that the LSPR absorption wavelength can be easily tuned from 950 to 735 nm by changing the sputtering power of MoO₃ of the (Ag)_x(MoO₃)_y composite. This shows that LSPR can be precisely adjusted by increasing the semiconductor content and even the carrier density. In addition, the carrier density was measured by Hall effect to investigate the SERS intensity change caused by electromagnetic (EM) enhancement, and obtain the relationship between the two. The findings of this work provide an idea for tunable LSPR and the research of EM contributions to SERS.