The invention discloses an assembly type ultrahigh heavy-load portal crane comprising two groups of portal crane beams, a crown block and a winch. The assembly type ultrahigh heavy-load portal crane is characterized in that four travelling wheels are connected to the undersides of the two groups of portal crane beams in a positioning way; a landing leg of the assembly type ultrahigh heavy-load portal crane is in a box type frame structure and assembled and connected by adopting universal rod bodies; the lower end of the landing leg is connected with a lower supporting boot in the positioning way; the lower supporting boot is connected with a bearing platform to be immobilized; the upper end of the landing leg is connected with an upper supporting boot in the positioning way; a horizontal spreader beam is connected to the upside of the upper supporting boot in the positioning way, and two parallel longitudinal spreader beams are connected to the upside of the horizontal spreader beam in the positioning way; the two parallel longitudinal spreader beams are connected with steel rails in the positioning way; and the four travelling wheels connected to the undersides of the two groups of portal crane beams in the positioning way are matched with the steel rails. The invention can carry out assembly according to different lifting heights and loads, has the advantages of simple structure, and higher integral structure stability, saves the cost, is fast to assemble and easy and flexible to operate.