The invention relates to an open type built-in stainless steel thermometal spiral composite pipe forming device mainly consisting of a forming mould (1) and a forming angle regulator (2), wherein support frames (11) and supports (19) are fixedly connected into a support structure of the forming mould (1), a rolling shaft (12) is installed between the support frames (11) through rolling shaft bearings (13), a ball support sleeve (16) of balls (12) is sleeved on the outer circumferential face of an inner support sleeve (17), balls (15) are spirally and uniformly distributed on the ball supporting sleeve (16) along the circumference and contact with the inner circumferential face of a forming pipe (30) which is made of a metal strap material (31) between the balls (15) and the balls (12) in a spiral coiling and forming mode, and the forming angle regulator (2) is used for regulating the forming angle of the forming mould (1). The invention is used for forming pipes with various wall thicknesses, and has the advantages of simple structure, low manufactured cost and simple and easy use, maintenance and repair.