Building structure and construction method thereof

The invention provides a building structure and a construction method thereof. The building structure comprises a main structure unit (10) and multiple roof truss structure units (20). The main structure unit (10) comprises steel columns (1), H-shaped steel beams (2), inner walls (3) and outer walls (4). Each roof truss structure unit (20) comprises a lower chord (201), an upper chord (202), a base web member (203), a first connecting piece (20a) and a second connecting piece (20b); the base web member (203) is arranged at an intersection point of the lower chord (201) and a middle H-section steel beam (22); the base web member (203) is fixedly connected to the middle H-section steel beam (22) through the first connecting piece (20a); and the second connecting piece (20b) is used for connecting the end portion of the lower chord (201), the corresponding side H-section steel beam (21) and the corresponding outer wall (4). According to the invention, the stability and bearing capability are guaranteed, the convenience of the installation for the main structure unit and a roof truss is effectively improved, and the stability of the connection of the roof truss and the main structure unit is improved.