The invention relates to the field of deep chemical milling of titanium-alloy large-scale cylindrical parts, in particular to a deep chemical milling method of TA12 and TA15 titanium-alloy large-scale structural components. The deep chemical milling method comprises the following technological lines: degreasing, washing, pickling, washing, coating with a protecting adhesive, marking, removing a protecting adhesive film on a to-be-milled surface, chemically milling and conducting vibrating finishing. The method comprises the following steps: a titanium-alloy cylindrical part is processed into a thin-walled grid rib by adopting a deep chemical milling technology, and the thin-walled grid rib is primarily marked and chemically milled to obtain a chemical milling machine case shell with all mounting bases. The manufacturing of integral, thin-walled and grid-shaped titanium-alloy large-scale cylindrical structural components is completed by adopting the titanium-alloy deep chemical milling technology, and the requirement that the large-scale cylindrical parts are chemically milled to form the grid-shaped structure is met; and deformation, caused by machining, is avoided fundamentally, the problem of low strength caused by welding is solved, the overall rigidity of the component is improved, and besides, the production cycle is shortened, and the structural weight is reduced.