The invention discloses an evacuation escape channel of a steel platform mould frame system and a construction method for the evacuation escape channel, relates to the technical field of building construction equipment, and aims to solve the problem that potential safety hazard exist due to the fact that a taking-down scaffold of a current steel platform is limited in length, and construction staff evacuates and escapes by virtue of a construction elevator in the core tube. The evacuation escape channel is formed by fixedly connecting a plurality of standard stair sections end to end, wherein each standard stair section comprises two vertical rods which are in parallel arranged, and a plurality of cross rods which are arranged at intervals and are fixedly connected between two vertical rods; the top end of the evacuation escape channel is fixedly connected to the bottom end of an inner hanging scaffold of the steel platform and is communicated with the inner hanging scaffold; and the bottom end of the evacuation escape channel is communicated with permanent structure stairs in the core barrel. The construction method comprises the following steps: fixedly connecting the top end of the evacuation escape channel between the inner hanging scaffold of the steel platform and the permanent structure stairs in the core barrel; and every time lifting the steel platform by one layer, immediately constructing one layer of the permanent structure stairs in the core barrel, so that the bottom of the lifted evacuation escape channel is communicated with the permanent structure stairs.