Partial substitution of iodate anions in La(IO3)3 by OH- or NO3- anion led to acentric La3(IO3)8(OH) and chiral La(IO3)2(NO3). The structure of La3(IO3)8(OH) can be seen as a complex three-dimensional (3D) network composed of two-dimensional [La3(IO3)2(OH)]6+ cationic layers that are further bridged by remaining iodate anions, or alternatively as a 3D network composed of one-dimensional [La3(IO3)6(OH)]2+ cationic columns being further interconnected by additional iodate anions, while the structure of La(IO3)2(NO3) can be seen as a novel 3D structure with planar NO3 groups serving as linkage between the [La3(IO3)6]3+ triple layers. Compared to La(IO3)3, both compounds show considerably wide band gaps and enhanced thermal stability. La(IO3)2(NO3) shows a moderate second harmonic generation (SHG) response of ∼0.6 times that of KDP (KH2PO4), a wide band gap of 4.23 eV, and a high LDT value (22 × AgGaS2). Optical property measurements, thermal analysis, as well as theoretical calculations on SHG origin, were performed. It can be deduced that partial substitution of iodate anions can be a facile route to design new noncentrosymmetric metal iodates with novel structure and potential application.