Provided is a manufacturing method of an engine inlet. The process method comprises the steps of uncapping subsection casting, casting pre-welding machining, vacuum electron jet assembling and welding, sizing destressing vacuum annealing, overall machining, hydrostatic testing and overall precise machining; an engine thin-wall titanium alloy component with the profile of a surface being less than or equal to 0.1mm, the surface roughness being less than or equal to Ra3.2, the dimensional precision being less than or equal to 0.2mm, and the form and location tolerance meeting design requirements is machined and manufactured. The manufacturing method overcomes defects in the prior art, meets all design requirements, resolves the problems of deformation, poor surface quality and poor dimensional precision which cannot be overcome by other machining methods, and is advanced and reasonable in technological process, smooth in technological production line, and especially suitable for developing and producing various engine thin-wall titanium alloy components.