X-ray combined with short-wavelength infrared (SWIR) phosphors, that can make full advantage of the deeper tissue penetration of SWIR light, can be used as a fluorescent probe to realize biological imaging of deep tissues; they are, however, limited by their lower luminescence efficiency. Here, we describe a strategy to synthesize highly efficient SWIR luminescence phosphor based on the efficient energy transfer process between charge transfer state (CTS) of Yb3+ and the 6IJ levels of Gd3+ as well as Gd3+-Gd3+. This allows us to achieve 813.8 mW/m2 of SWIR luminescence power in Yb3+-BaGd0.6Y0.4ZnO5 (BGYZ). Our results highlight that this approach to enhance SWIR luminescence may provide new opportunities for the deep-tissue biological imaging.