The invention belongs to the technical field of steam turbine equipment, and particularly relates to a dehumidification stage gradual expanding type steam cylinder hydrophobic structure. The dehumidification stage gradual expanding type steam cylinder hydrophobic structure comprises a high-pressure air cylinder body and further comprises a gradual expanding type air cylinder hydrophobic structure,the gradual expanding type air cylinder hydrophobic structure is fixedly mounted on the bottom of a dehumidification stage cavity of the high-pressure air cylinder body, a thread connection hole is machined in the bottom of the dehumidification stage cavity, the gradual expanding type air cylinder hydrophobic structure is connected with the thread connection hole in the bottom of the dehumidification stage cavity through an outre thread, and the gradual expanding type air cylinder hydrophobic structure is in threaded connection and then welded to the high-pressure air cylinder, and a conicalthrough hole used for draining is machined in the gradual expanding type air cylinder hydrophobic structure; the hole diameter size of the conical through hole can ensure that water steam in the dehumidification stage cavity can smoothly flow out of the air cylinder. Through the hydrophobic structure, dehumidification stage portion condensate water in the steam cylinder can better flow out, dehumidification stage wet gas losses brought by water increasing in the dehumidification stage area steam water can be effectively reduced, steam enthalpy value in the later stages can be increased, and the efficiency of a steam turbine can be improved.