Fluorooxoborates as potential deep ultraviolet (DUV) nonlinear optical (NLO) materials have exhibited diverse structures and NLO properties with metal cationic changes. Herein, the general mechanisms of metal cations on band gaps and optical properties in a series of typical fluorooxoborates have been clarified. It reveals that the framework of the emblematic 18-membered ring oxyfluorides has the flexibility of being able to contain different cations spanning from alkali to d(10) metals by investigating the stability of the artificial CdB5O7F3 structure. Besides, introducing d(10) metal cations can enhance the second harmonic generation (3.1xKH(2)PO(4) (KDP), d(36)=0.39 pm V-1) and also keep a DUV spectral transparency (E-g>6.2 eV). Thus, the d(10)-containing fluorooxoborate exhibits a great potential to be a new DUV optical material for nonlinear light-matter interactions.