A promising phosphors Ca2Al2SiO7:Tm3+,Dy3+ were synthesized by conventional high temperature sintering. Phase identification, crystal structure refinement, luminescence properties, energy transfer mechanism of Tm3+→Dy3+, and CIE color coordinates were investigated systematically. The phase structure of prepared phosphors were confirmed by XRD analysis and structure refinement. From the results of photoluminescence, the CASO: Tm3+ phosphors showed intense blue light emission peaks at 454nm (the transition from 1D2 to 3F4), while CASO:Dy3+ phosphors exhibited predominant yellow light emission peaks at 581nm (the transition from 4F9/2 to 6H13/2), implying that the Dy3+ were located in the non-inverted symmetric site of the CASO host lattice. Meanwhile, the results exhibited that the optimal doping content of Dy3+ was 0.01, and the mechanism of concentration quenching was the nearest-neighbor ions interaction. The overlapped emission (Tm3+)/excitation (Dy3+) spectra, decay curves and the energy level scheme about CASO:Tm3+,Dy3+ confirmed the energy transfer of Tm3+→Dy3+. Moreover, by adjusting Tm3+/Dy3+ ions concentration, the intensities of yellow emission for Dy3+ and blue emission for Tm3+ could be adjusted to tune the emitting color of CASO:Tm3+, Dy3+. Excited by the most effective excitation wavelength at 355nm, the CIE coordinates (0.3422, 0.3262) of phosphor CASO:0.01Tm3+, 0.01Dy3+ was closest to the coordinates of white chromaticity (0.33, 0.33). Results indicate that the potential value of phosphors Ca2Al2SiO7:Tm3+,Dy3+ are used as a single-phase color-adjustable phosphors for NUV pumped white-LEDs.