The present disclosure provides a block assembly applied not only to an educational purpose for children but also to a model architecture and a simple real building, etc. In one aspect, there is provided a block assembly comprising: a plurality of first-rods, each first-rod having a first cross sectional area, wherein each first-rod is solid or hollow; a plurality of second-rods, each second-rod having a second cross sectional area larger than the first cross sectional area, wherein each second-rod is solid or hollow; a plurality of H shaped beams, each having a H shaped cross section; and at least one of first to fourth unit blocks.