A multidimensional front-and-back-sides-freely-buildable building block toy construction element, comprising a second module; wherein the second module is adapted to be coupled into a first module; a front side of the first module is provided with a plurality of first coupling posts (r), and a back side of the first module is provided with a plurality of second coupling posts (t); a front side of the second module is provided with a plurality of third coupling posts (s); each third coupling post (s) of the plurality of third coupling posts is a cylinder penetrating the second module; a back side of the second module is provided with a concave surface; a plurality of fourth coupling posts (u) are disposed on and protrude from the concave surface; the plurality of fourth coupling posts are distributed in columns located in a middle equally dividing two adjacent columns of the plurality of third coupling posts (s); each of the plurality of fourth coupling posts (u) is located in a middle equally dividing two third coupling posts (s) of the plurality of third coupling posts; an outer diameter of each first coupling post (r) of the plurality of first coupling posts is a first size; an outer diameter of each second coupling post (t) of the plurality of second coupling posts, an outer diameter of each third coupling post (s) of the plurality of third coupling posts and an outer diameter of each fourth coupling post (u) of the plurality of fourth coupling posts are all a second size, characterized in that a nearest distance between peripheries of two diagonally adjacent third coupling posts (s) of the plurality of third coupling posts on the front side of the second module is the second size; a nearest distance between peripheries of two diagonally adjacent fourth coupling posts (u) of the plurality of fourth coupling posts on the back side of the second module is the second size; and the front side of the second module is adapted to be coupled into a back side of an adjacent second module; and a front side of the second module is adapted to be coupled into the front side of the adjacent second module. wherein the second module is adapted to be coupled into a first module; a front side of the first module is provided with a plurality of first coupling posts (r), and a back side of the first module is provided with a plurality of second coupling posts (t); a front side of the second module is provided with a plurality of third coupling posts (s); each third coupling post (s) of the plurality of third coupling posts is a cylinder penetrating the second module; a back side of the second module is provided with a concave surface; a plurality of fourth coupling posts (u) are disposed on and protrude from the concave surface; the plurality of fourth coupling posts are distributed in columns located in a middle equally dividing two adjacent columns of the plurality of third coupling posts (s); each of the plurality of fourth coupling posts (u) is located in a middle equally dividing two third coupling posts (s) of the plurality of third coupling posts; an outer diameter of each first coupling post (r) of the plurality of first coupling posts is a first size; an outer diameter of each second coupling post (t) of the plurality of second coupling posts, an outer diameter of each third coupling post (s) of the plurality of third coupling posts and an outer diameter of each fourth coupling post (u) of the plurality of fourth coupling posts are all a second size, characterized in that a nearest distance between peripheries of two diagonally adjacent third coupling posts (s) of the plurality of third coupling posts on the front side of the second module is the second size; a nearest distance between peripheries of two diagonally adjacent fourth coupling posts (u) of the plurality of fourth coupling posts on the back side of the second module is the second size; and the front side of the second module is adapted to be coupled into a back side of an adjacent second module; and a front side of the second module is adapted to be coupled into the front side of the adjacent second module.