A new phase of the compound, Na3ZnB5O10, crystallizes in orthorhombic space group Pbca (No. 61) with lattice constants a = 7.8923(4) angstrom, b = 12.2437(7) angstrom, c = 18.0636(11) angstrom, Z = 8. The Na3ZnB5O10 structure exhibits that the isolated B5O10 groups are bridged by ZnO4 tetrahedra and NaOn (n = 5,7) polyhedra through the vertex oxygen atoms to form an infinite three-dimensional structure. Functional groups in the sample were identified by IR spectrum. Na3ZnB5O10 has a phase transition, and exhibits a short-wavelength absorption onset below 190 nm.