Abstract: A hydro-extruding forming process of Y-shaped three-way tube based on hydraulic bulging and extrusion forming was proposed. The forming process was simulated based on the software Abaqus. The main defects in tube forming process, and affecting factors such as internal pressure, loading path and friction coefficient on the quality of tube forming were studied. The results show that the main quality problems of the tube are uneven wall thickness distribution and wrinkling.The internal pressure plays a decisive role in wrinkling, and when the internal pressure is above 30 MPa, the wrinkles disappear. When the internal pressure is 35 MPa, the forming quality is good. The smaller the friction coefficient is, the smaller the wall thickness difference is. A suitable internal pressure loading path can improve the wall thickness distribution of the tube.