The present disclosure provides a wire and arc additive manufacturing (WAAM) method for a titanium alloy. The method includes the following steps: step 1: performing a WAAM process assisted by cooling and rolling; step 2: milling side and top surfaces of an additive part; step 3: performing, by friction stir processing (FSP) equipment, an FSP process on the additive part, and applying cooling and rolling to a side wall of the additive part through a cooling and rolling device during the FSP process; step 4: finish-milling the top surface of the additive part for a WAAM process in the next step; and step 5: repeating the above steps cyclically until final forming of the part is finished. This WAAM method completely breaks dendritic structures and refines grains in the WAAM process of the titanium alloy, thereby effectively repairing defects such as pores and cracks.