Abstract: In order to solve the forming problem of no-mandrel bending of composite tubes, the finite element model of no-mandrel bending of TC4 titanium alloy/304 stainless steel composite tubes was established and the bending test was carried out by taking the change rate of wall thickness of the elbow and the rate of change of the short axis as the forming indexes, and the influence of bending angle, bending speed and wall thickness ratio of inner and outer tubes on the bending formability were studied. The results show that with the increase of bending speed and bending angle, the rate of change of the short axis and the rate of change of wall thickness are positively correlated, and the thickening rate of wall thickness is always greater than the thinning rate of wall thickness. With the change of the ratio of wall thickness on the inner and outer sides of the tube, the ratio of stainless steel increases, and the change rate of the wall thickness of the inner and outer sides of bending and the change rate of the short axis show a negative correlation trend. By selecting the appropriate bending process, a qualified composite bend with a relative bending radius of 2 is finally bent.