A multifunctional breast cancer affected limb fixing support belt comprises a back towel, a first front towel and a second front towel. One side of the back towel is connected with the first towel through an elastic belt, the other side of the back towel is connected with the second front towel through an elastic belt, an adhesive male fastener is arranged on the first front towel, a drainage bag fixing bag and a support belt are arranged on the lower portion of the first front towel, the tail end of the support belt is connected with a shoulder belt, an adhesive female fastener fastened with the adhesive male fastener is arranged on the second front towel, a buckle fastener is arranged on the upper portion of the second front towel, and an adjusting fastener for adjusting the length of the shoulder belt is arranged on the buckle fastener. Random swing of an affected limb can be effectively controlled, the influence of postoperative premature affected side upper arm movement on armpit wound healing is prevented, pulling and sliding of a chest flap can be prevented, a chest belt can be correctly pressurized and bound, and a skin flap is matched with a chest wall blood vessel as soon as possible. When a patient does off-bed activity, the affected limb can be placed at a functional position by the aid of the support belt, a drainage bag can be placed in the drainage bag fixing bag, and drainage tube dislocation caused by pulling is prevented.