The invention relates to a varifocal photoetching objective lens system, belongs to the technical field of optics and solves the problem that mask plate exposure patterns different in proportion cannot be exposed by a same existing photoetching objective lens. The varifocal photoetching objective lens system sequentially comprises an object surface, a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group and an image surface from the object surface to the image surface. The object surface is a plane where a mask plate is located, the first lens group is used for fixing the distance between the object surface and a first lens of the varifocal system, the second lens group functions in changing the focal of a photoetching objective lens and the size of the image surface, the third lens group functions in compensating moving of the image surface during moving of a zoom group so as to enable the image surface to be kept fixed during zooming, the fourth lens group is provided with a negative power, a fifth lens group is provided with a positive power, the fourth lens group and the fifth lens group form a rear fixing group which is used for guaranteeing constant distance between the last lens, close to one side of the image surface, of the photoetching objective lens and the image surface, and the image surface is a plane where an etching substrate is located.