The invention provides a catheter apparatus, which includes an integrally formed multi-lumen pipeline structure having a proximal end direction and a distal end direction, wherein the multi-lumen pipeline structure includes a tubular structure and multiple fluid flow pipe structures, and the tubular structure and the multiple fluid flow pipe structures are disposed along a first axial direction of the multi-lumen pipeline structure； at least one pipe sleeve membrane element wrapped on the outer periphery of the multi-lumen pipeline structure, wherein the at least one pipe sleeve membrane element includes a strengthening structure and/or a buffering structure； and a pointed end which is jointed with the multi-lumen pipeline structure and is tightly fastened with the multi-lumen pipeline structure. The invention further provides a brachytherapy system using the catheter apparatus, which can be used for treating intracavitary tumors such as esophageal cancer or the like.
