The invention discloses a process for constructing a metal roof of a building with super-large space. The process includes steps of 1), laying a steel lining plate on the lowermost layer of a roof structure; 2), laying a non-woven dustproof layer on the lining plate; 3), laying a glass wool sound absorbing layer on the non-woven dustproof layer and compacting the glass wool sound absorbing layer; 4), laying a vapor barrier on the glass wool sound absorbing layer; 5), laying lower-layer glass wool on the vapor barrier and compacting the lower-layer glass wool; 6), laying upper-layer heat-insulation rock wool on the lower-layer glass wool and compacting the upper-layer heat-insulation rock wool; 7), mounting support purline; 8), laying supporting steel plates; 9), laying a gypsum fiber board; 10), laying a waterproof vapor-permeable layer on the gypsum fiber board; 11), laying an ultrafine glass cotton anti-noise layer on the waterproof vapor-permeable layer; 12), mounting an aluminum-magnesium-manganese alloy roof panel on the uppermost layer of the roof structure. The process for constructing the metal roof has the advantages that a waterproof effect of the metal roof is improved, water seepage at pierced positions is prevented, outdoor noise is prevented from being transmitted into a room, and heat-insulation, damp-proof and vapor-permeable effects of the metal roof are improved.