The invention provides an optical
system, an
operating microscope and an adjusting method. The optical
system comprises an objective lens group; the continuous
zoom lens group is arranged on the image side of the objective lens group; the objective lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged on the same
optical axis from the object side, each of the first lens and the fifth lens has negative focal power, each of the second lens, the third lens and the fourth lens has positive focal power, the first lens and the second lens are glued to form a first glued lens, and the second lens and the fifth lens are glued to form a second glued lens; the object side surface of the first cemented lens is a
concave surface, the image side surface of the first cemented lens is a convex surface, the third lens is a biconvex lens, the fourth lens and the fifth lens are cemented to form a second cemented lens, the object side surface of the second cemented lens is a convex surface, and the image side surface of the second cemented lens is a
concave surface; the objective lens group meets the following relational expression: low-aberration and high-resolution imaging is realized through the
system and the method.