A catheter fixer used in a plasma exchange for a patient with severe hepatitis is disclosed, which mainly solves the problem of the absence of a proper catheter fixing device while performing a plasma exchange on a patient with severe hepatitis at present. The catheter fixer used in a plasma exchange for a patient with severe hepatitis is characterized in that: the bottom of a silica gel plate is an arc surface, and the upper part of the silica gel plate is provided with spaced longitudinal insertion holes; the cross sections of the longitudinal insertion holes are trapezoids, and N-pole magnetic stripes are disposed at the bottom ends in the longitudinal insertion holes; a catheter embedding insertion frame is further provided and is composed of a location tube and a trapezoidal insertion sheet after being connected; a one-way clack is disposed in the location tube, and S-pole magnetic stripes are bound at the bottom end of the trapezoidal insertion sheet; the section shape of the trapezoidal insertion sheet is matched with those of the longitudinal insertion holes; and left and right Velcro patches are fixed on the end parts of elastic tensioning belts at the left and right ends of the silica gel plate respectively. The catheter fixer is very simple in structure, convenient in operation, and capable of adjusting the fixed space of a catheter according to the specific condition of the patient; and after the catheter is located in a surgery, the space positions of the catheter and a human body cannot be changed any more, thereby ensuring the normal process of the surgery.