The influence of doping the transition metal Zn (II) on thermal property of gel grown lead iodate crystals was studied using the thermo analytical techniques, which included TG, DTA, and DTG. It was found that, decomposition temperature of lead iodate crystal is shifted to higher value by 18°C. A close observation of FT-IR and Raman profiles of samples reveals presence of iodate group. It appears that the crystal undergoes considerable lattice stress as a result of doping the bivalent zinc. The absence of water of hydration in the grown crystals was confirmed by FT-IR and thermal analysis.