The utility model relates to the technical field of solar equipment, in particular to a heat absorbing body of a solar flat plate collector, which comprises a heat absorbing plate, a heat transfer flow channel, a first heat collecting pipe, a second heat collecting pipe, a heat collecting pipe joint and an n-shaped connecting piece, the heat absorption plate is of a rectangular structure, the heattransfer flow channels are arranged on the heat absorption plate in parallel and are in a grid shape, the upper ends and the lower ends of the heat transfer flow channels are connected with the firstheat collection pipe and the second heat collection pipe respectively, and the first heat collection pipe and the second heat collection pipe are of a right-angle structure and are conveyed out froman upper frame of the heat absorption plate respectively. Heat collecting pipe joints are arranged at outlets of the first heat collecting pipe and the second heat collecting pipe; a first heat collecting pipe of the heat absorbing body of the first solar flat plate collector and a second heat collecting pipe of the heat absorbing body of the second solar flat plate collector are connected and fixed between the heat absorbing bodies of the two solar flat plate collectors through n-shaped connecting pieces; the telescopic performance is excellent, and the telescopic amount of the system due toexpansion caused by heat and contraction caused by cold can be effectively buffered.