The invention relates to a steel structure construction platform and a large gradient self-climbing system and a telescopic platform system thereof. The large gradient self-climbing system comprises a suspension seat, a machine frame, a guide rail and a supporting wheel, wherein one end of the supporting wheel is fixedly connected with the machine frame; the other end of the supporting wheel is supported on a steel structure in a scrollable or slidable way; the respective angle of the guide rail and the machine frame relative to the steel structure is changed via a mode that the length of the supporting wheel is changed; the guide rail and the machine frame can rotate around the suspension seat; moreover, the rotation axes of the guide rail and the machine frame are the same; the guide rail and the machine frame implement alternate climbing through a transmission and anti-falling device arranged between the guide rail and the machine frame; the telescopic platform system comprises a male platform and a female platform; the male platform can retract relative to the female platform, so that the size of the telescopic platform system is adjusted; at the moment, the self-displacement is realized to stride over a barrier. By the adoption of the steel structure construction platform and the large gradient self-climbing system and the telescopic platform system thereof, the use of a tower crane can be reduced and the trouble of manual displacement can be prevented.