The first example of SHG crystal in the metal bromates containing pi-conjugated planar triangle systems, namely, Pb-4(OH)(4)(BrO3)(3)(NO3), was successfully synthesized via the hydrothermal method. Furthermore, a single crystal of centrosymmetric Pb8O(OH)(6)(BrO3)(6)(NO3)(2)center dot H2O was also obtained. Both compounds contain similar [Pb-4(OH)(4)] cubane-like tetranuclear clusters, but they display different one-dimensional (1D) chain structures. Pb-4(OH)(4)(BrO3)(3)(NO3) features a zigzag [Pb-4(OH)(4)(BrO3)(3)](+) 1D chain, while Pb8O(OH)(6)(BrO3)(6)(NO3)(2)center dot H2O is composed of two different orthogonal chains: the linear [Pb-4(OH)(4)(BrO3)(2)](2+) 1D chain along the b-axis and the zigzag [Pb4O2(OH)(2)(BrO3)(4)](2-) 1D chain along the a-axis. The NO3 planar triangles of the compounds are all isolated and located in the spaces of the structures. Pb-4(OH)(4)(BrO3)(3)(NO3) exhibits the first example of SHG crystal in the metal bromates with pi-conjugated planar triangle. The second-harmonic generation (SHG) efficiency of Pb-4(OH)(4)(BrO3)(3)(NO3) is approximately equal to that of KDP and it is phase-matchable. Dipole moment and theory calculations indicate that BrO3, NO3, and PbO4 groups are the origin of its SHG efficiency, although some of the contributions cancel each other out.