Nanosized $SnO_2$ particles were synthesized by homogeneous precipitation method using tin chloride ($SnCl_4{cdot}5H_{2}O$) and urea ($CO(NH_2)_2$). The powders were heated at $500^{circ}C$ and $600^{circ}C$ for 2h. The crystal structure, microstructure, thermal behavior, specific surface area were analyzed using XRD, FE-SEM, TGA and BET, respectively. The initial resistance and the $H_2$ sensing properties were measured as a function of ${Sb_2}{O_3}$ and Pd doping concentrations. The resistance was decreased with the addition of ${Sb_2}{O_3}$ and the sensitivity for $H_2$ gas was increased with the addition of Pd. Thus, the optimum $H_2$ gas sensing property was obtained in the 0.25.mol% ${Sb_2}{O_3}$ and 1.w% added $SnO_2$ powders.