An insert-and-twist building block structure includes a connection bar and a connection terminal unit. The connection bar has an end from which a combination projection section extends and has a conic shape. The combination projection section has an external circumferential surface formed with a bead ring including multiple raised beads intermittently arranged in a ring configuration. The connection terminal unit includes a connection terminal having an end inward recessed to form a combination cavity in a conic shape. The combination cavity has an internal circumferential surface formed with a groove ring including multiple recessed grooves intermittently arranged in a ring configuration. The recessed grooves each a middle portion forming a deep trough section and two ends each forming a shallow trough section, and a depth is decreased from the deep trough section toward the shallow trough sections.