The invention discloses a heat-collecting device for recovering radiant energy waste heat on the wall surface of a high-temperature cylinder of a cement rotary kiln, which comprises a plurality of collector assemblies, wherein each collector assembly is formed by arranging at least two collector unit structures around a rotary kiln cylinder; each collector unit structure consists of a collector unit main body, two connecting pipes, four transition pipes and a channel steel frame; the transition pipe on one collector unit main body is communicated with the transition pipe on the other collector unit main body, so that the at least two collector unit structures are connected together; and a closure plate is arranged at a pipe orifice, which is not communicated with other transition pipes, at one end of the transition pipes on the two collector unit main bodies on the outermost side, so the collector assemblies are formed finally. The device has a simple structure and low cost, can ensure heat-collecting efficiency, and does not influence the production of cement simultaneously.