SnO₂ nanoparticles have been synthesized via sol-gel method in different annealing temperatures. TEM, FESEM and XRD techniques have been used to investigate the structure and morphology of SnO₂ nanoparticles. The XRD pattern analysis shows all samples are single phase. XRD patterns show as the annealing temperature increases, the peaks become sharper which is related to the increase in the crystallite size of nanoparticles and enhancing the crystalline order and reducing lattice strain. The Williamson-Hall analysis and Halder-Wagner method were used to study the individual contributions of crystallite sizes and lattice strain to the peak broadening of nanoparticles. The physical parameters such as strain, stress and energy density values were calculated for three major reflection peaks of XRD patterns. Williamson-Hall analysis of XRD patterns show that increasing the annealing temperature causes the crystallite size to increase and to reduce lattice strain. TEM and FESEM images showed that by increasing temperature, nanoparticle size increases.