A modulated structure with symmetrical characteristic higher than three-dimensional is a fascinating crystallographic type, and it is randomly encountered by researchers. Herein, we prepared 0.1 mm level single crystals of Na3La(VO4)2 and determined its structure to be a (3 + 1)-dimensional modulated structure using the X-ray diffraction analysis method for single crystals. Its super space group was determined to be Pca21(0β0)000. On the other hand, we introduced Tb3+ into the Na3La(VO4)2 host lattice to fabricate phosphors Na3La1-x(VO4)2:xTb3+ and studied their photoluminescence properties. Interestingly, for the strong absorption of the Na3La(VO4)2 host lattice in the range of 200-400 nm, the traditional 330-385 nm light is unable to efficiently excite Tb3+ ions in the Na3La(VO4)2 host to generate luminescence of Tb3+. Instead, Na3La1-x(VO4)2:xTb3+ is suitable to be excited by 487 nm to generate emitting light at 543, 584, and 622 nm, due to Tb3+ characteristic 4f → 4f transitions of 5D4 → 7FJ (J = 5, 4, 3). Hence, the Tb3+-doped Na3La(VO4)2 phosphors have potential applications for white-light-emitting diodes.