The utility model relates to a beam die fixing device capable of being adjusted according to change of a beam cross-section. The beam die fixing device comprises a wall-penetrating screw rod, a width adjusting mechanism and a height adjusting mechanism. The height adjusting mechanism comprises two columns of vertical rods disposed on the outside of a side die master framework, each column being formed through connection of two vertical rods by a connecting member; cushion blocks are filled between the tops and bottoms of the two vertical rods of each column for forming a channel; the two vertical rods are connected by the connecting member for forming an ensemble; two ends of the wall-penetrating screw rod are fixed by butterfly nuts; the width adjusting mechanism comprises a casing pipe, an adjusting screw rod and an adjusting clamp, wherein the adjusting screw rod is inserted in the casing pipe and is tightly clamped by the adjusting clamp at a joint; and the width adjusting mechanism and the height adjusting mechanism are connected into a whole through the base plates welded to the bottoms of the vertical rods. The beam die fixing device can be adjusted according to the change of the width and height of a beam, is highly universal, is reusable, causes no damage to die plates, and is widely applicable to die plate fixation of cast-in-place concrete beams.