Abstract: A building system used for constructing a building is disclosed in the present invention. The building system includes: a first block, a corner block and a connection block interlocking with each other for constructing the building; wherein, dimensional relations between the first block, the corner block and the connection block satisfying the following conditions: Lco=L+W; Wco=½L+W; Lci=L; Wci=½L; Lcb=½L; Wcb=W; Wherein, is a length of the first block; W is a width of the first block; Lco is an outer length of the corner block; Wco is an outer width of the corner block; Lci is an inner length of the corner block; Wci is an inner width of the corner block; Lcb is a length of the connection block; Wcb is a width of the connection block.

Abstract: A building block and a building system used for construction a building are disclosed in the present invention. The building block includes: an inner face, an outer face, an upper face having a base face and a projection protruding upward from the base face, wherein the projection extending longitudinally for the entire length of the upper face; a lower face having a complementary groove for interlocking with the projection of a cooperating interengaging building block; a first end; a second end; each of the first end and the second end has a header face, which is substantially one of a planar face, a male header face and a female header face, the male header face of the building block interlocking with the female header face of a cooperating interengaging building block; the cooperating interengaging building block is substantially similar to the building block.