The utility model relates to a united circulation three-cylinder three-pressure extraction steam turbine which aims to solve the problems of low economical efficiency, low energy utilization rate and waste of energy of a 9F-level united circulation steam turbine in the prior art. The united circulation three-cylinder three-pressure extraction steam turbine comprises a low-pressure cylinder, a first bearing box, a communicating pipe, a rotor, a high-pressure cylinder, an intermediate-pressure cylinder, a second bearing box, a third bearing box, a fourth bearing box and an intermediate-pressure rotor steam cooling system, wherein the first bearing box, the high-pressure cylinder, the second bearing box, the intermediate-pressure cylinder, the third bearing box, the low-pressure cylinder and the fourth bearing box are sleeved on the rotor and are connected with one another sequentially; the intermediate-pressure rotor steam cooling system is communicated with the high-pressure cylinder and the intermediate-pressure cylinder respectively. The united circulation three-cylinder three-pressure extraction steam turbine can be used for an adjustable extraction steam heat supply unit.