The invention discloses a segmental hoisting process of an ultra-large-span steel truss. The process includes the following steps that (1) vertical lifting devices of the steel truss are built; (2) the whole steel truss is divided into a plurality of sections, and each section of the steel truss is assembled on the ground; (3) the sections of the steel truss are placed on the corresponding vertical lifting devices respectively; (4) each section of the steel truss is sequentially lifted to a proper elevation and is fixed through a temporary fixing supporting device; (5) after measurement and collection are carried out, the sections of the steel truss are combined to form a whole aloft. The segmental hoisting process effectively solves the problem that installation is limited by conditions, is simple and convenient to operate, safe and reliable, guarantees installation safety and quality, and meanwhile is economical, reasonable and advanced in technique. Compared with a common large hoister hanging and spare part installation process, the segmental hoisting process is safe, convenient to achieve, economical and efficient.