The invention discloses a large-arc-radius round slab blank compatible continuous casting machine and a process thereof. The purpose is to produce continuous casting slab blanks with the macrostructures and the density meeting the quality standard. On the aspect of equipment, the slab blank continuous casting machine with the arc radius being 16.485 m and the cross section being 200mm*(550-850)mmis additionally arranged on the basis of existing radius being 16.5 m and existing large round blank cross sections being phi600/700/800; and the slab blank continuous casting machine is composed of atundish of a round blank continuous casting machine, a crystallizer, fan-shaped sections, a secondary cooling steam exhaust part, a straightening and withdrawal machine and an automatic program human-computer interface after modification. On the aspect of the process, the position of a submersed nozzle of the tundish, the size and tape value of the crystallizer and the opening degree of the slabblank fan-shaped sections are designed, the allowable pulling speed of casting blanks, the secondary cooling parameter and mode and the divisional distribution of secondary cooling water nozzles are adjusted, and the pressure of the straightening and withdrawal machine is changed. Multi-section switchable pouring is achieved, and the density of the continuous casting slab blanks is as high as 7.924 t/m<3> after measurement and is far higher than 7.850 t/m<3> of conventional slab blanks; and the center porosity of the macrostructures is not higher than 1.5 grade, and the middle cracking is nothigher than 1.5 grade.