The present invention relates to a target assembly and its manufacturing method. The target assembly includes a first target, a base, and a window. Wherein, the first target has the ability to generate first radiation when it is hit by a beam, the base is used to support the first target, and the window is permeable to at least part of the beam. The window and the base form at least part of a sealed chamber in which the first target is located, wherein the sealed chamber is filled with air having a normal oxygen content or a lower than normal oxygen content. Compared with the traditional solution, the target assembly of the present invention is assembled in the air, which simplifies the manufacturing process. The target in the target assembly is in a sealed environment, and will not undergo further oxidation reaction with the air outside the sealed environment, nor will it cause mass loss due to volatilization of oxidation products, thereby improving its service life.