Two polar molybdenum(VI) iodates(V), NH4[MoO3(IO3)] (1) and KRb[(MoO3)(2)(IO3)(2)] (2), have been prepared by a hydrothermal method. They crystallize in noncentrosymmetric (NCS) space groups Pna2(1) and Cc, respectively. Structurally, it is interesting that compound 2 has an exclusive one-dimensional [IO3](-) chain based on corner sharing [IO4](3-) units in all iodates(V). As for the properties, both compounds exhibit large second-harmonic generation responses of 4.7 X KH2PO4 (KDP) for compound 1 and 8.5 X KDP for compound 2 with phase-matching behavior. These results are in good agreement with the results of the theoretical calculations. In addition, both compounds also possess large birefringences (Delta n) of 0.083 at 1064 nm and 0.146 at 1064 nm, respectively. These results indicate that the title compounds will have potential applications as nonlinear optical materials.