This letter assesses the origin of linear and planer micro-structural defects in SnO2 nanoparticles through high resolution transmission electron microscopy (HRTEM). For the purpose, SnO2 nanoparticles of size 5-15 nm are synthesized by chemical co-precipitation followed by calcinations. In the low temperature (200°C and 400°C) calcinations range no significant evidence of micro-structural defect are observed. Whereas, SnO2 nanoparticles calcined at 600°C shows better crystallinity with multiple 1-D linear defects along with 2-D planer defects. Contribution of size and strain effect causing such circumstances is illustrated in detail. Influence of these micro-structural defects on the luminescence properties of SnO2 nanoparticles is also elaborated in detail.