A portable intravenous bag positive pressure device includes a main body and an elastic positioning unit. The main body is to encircle the arm of a patient at an appropriate position with its adjustable positioning belt to secure the main body. An intravenous bag is placed into an accommodation space formed between a positioning seat of the main body and the elastic positioning unit. The elastic positioning unit applies positive pressure to the intravenous bag to continuously output an infusion liquid for infusion therapy. The device has a simple structure and is convenient for wearing and able to secure the intravenous bag firmly on the arm of the patient. It is beneficial for the patient to carry the intravenous bag and move around during infusion therapy.