The invention provides a block distributed single-shaft 3D printing device and a printing method thereof and relates to the technical field of building construction, aiming at solving the problems that the working efficiency of a single printing head of an existing 3D printing device is low and the precision is not high so that the construction requirements of large-size buildings cannot be met. The block distributed single-shaft 3D printing device comprises a climbing device and a printing device, wherein the climbing device can drive the printing device to climb or descend along a printed building; the printing device comprises a printing head transverse beam and a rail framework composed of a rail transverse beam and a connection beam; the two ends of the printing head transverse beam can slide along the rail framework; printing heads, which are synchronous with the printing head transverse beam, are densely distributed on the printing head transverse beam; building materials are sprayed out by the printing heads; when the printing head transverse beam moves every time, printing construction of a current cross section layer is finished; and a climbing guide rail is lengthened to a pre-set height, and the printing device is jacked to the height of one cross section layer to be printed on the building through controlling the climbing device, so that each cross section layer is gradually printed from bottom to top until printing construction of the whole building is finished.