Among the 21 pseudo-binary systems formed by alkali-metal iodates (including HIO3 and NH4IO3), there are 9 in which compounds can be synthesized in aqueous solutions or by powder-sintering, 6 which are mixtures of the constituents; and the rest of the systems can formed continuous solid solutions. The pseudo-binary systems KIO3-NHJO3, RbIO3 etc. were studied by means of thermal analysis (DTA, TG) and Xray diffraction, and were found to be of continuous solid solutions. With addtion of KIO3 or RbIO3, the phase transition temperature of NH4IO3 is decreased and its decomposition (at the same time burning) temperature is raised; the room temperature phase of NH4IO3 (monoclinic) is transformed gradually into cubic phase with increasing content of KIO3 or RbIO3. Samples in the binary systems with NH4IO3 as a component exhibit good pyroelectric property. In this paper, the stability and the change of lattice parameter with compositions of the solid solutions that were found in alkalimetal iodate binary systems were also discussed.