Constructing lanthanide doped semiconductor nanocrystals (Ln-SNCs) is a promising strategy for combining of bright, long-lived, and spectrally narrow Ln3+ emission, along with strong broadband absorption and low-phonon-energy crystalline environment of semiconductor to make new spectral-conversion nanophosphors. NaInS2 SNC is one of the most important host series for its high stability and non-toxicity as compared to those widely explored Ln doped perovskite SNCs. Such a family SNCs provide high cation coordination numbers (CN) of 6, which fulfills the cation the fundamental prerequisite for Ln3+ doping. However, the photoluminescence quantum yields (PL QYs) of Yb3+ doped NaInS2 are still below 8% in most SNCs thus far, restricting their further application in near-infrared (NIR) bio-probe. Here, we demonstrate a strategy for accessing Yb3+/Bi3+-codoped NaInS2 SNCs for strong NIR emission. In order to improve the NIR emission, we introduce Bi3+ ions to create new excitation channels, aiming at enhancing the ultra-violet (UV) and visible light absorption. Furthermore, an ZnS outer-layer growth on Ln-doped NaInS2:Bi passivates the surface of SNCs and suppresses the surface defect related non-radiative recombination losses. Our NaInS2:Yb/Bi@ZnS SNCs exhibit efficient NIR emission around 1000 nm with a notable PL QY of 9.5%, suggesting their potential applications in NIR bio-imaging.