The invention discloses a boiler drum longitudinally arranged chain grate hot water boiler, and relates to a hot water boiler to solve the problems that the conventional boiler has low thermal efficiency and high coal consumption, pipes are easy to block, and smoke discharging temperature is high. The boiler drum longitudinally arranged chain grate hot water boiler comprises a left longitudinal upper header, a right longitudinal upper header, a left longitudinal water tank, two first vertical water distributing pipes, two second vertical water distributing pipes, a plurality of upper transverse headers, a plurality of lower transverse headers, a front transverse header, a rear transverse header, a plurality of first water cooling wall pipes, a plurality of second water cooling wall pipes,a plurality of groups of third water cooling wall pipes, a plurality of groups of fourth water cooling wall pipes, a plurality of groups of fifth water cooling wall pipes, a plurality of groups of sixth water cooling wall pipes, a plurality of groups of upper convection banks, a plurality of groups of front convection banks, a plurality of groups of rear convection banks, and at least one convection economizer, wherein the front transverse header and the rear transverse header are communicated with a left coking prevention ark and a right coking prevention ark; adjacent upper boiler drums in a plurality of upper boiler drums, and the left longitudinal upper header and the right longitudinal upper header and the respectively adjacent upper boiler drums are communicated thorough the plurality of upper transverse headers. The boiler drum longitudinally arranged chain grate hot water boiler is used for central heating.