Cavitation bubbles occur easily at the head，shoulder and surface prominences of high-speed underwater vehicles. In this papers，the surface prominences are simplified into steps of a certain height without loss of generality. Based on the simplified vehicle model，2 types of double bubble interactions，which are interactions between shoulder bubble and step bubble，and interactions between shoulder bubble and tail bubble，are studied through numerical simulation method. With different angles of attack，there are differences in the process of interactions between shoulder bubble and step bubble，which can be divided into two types：interactions with large angle of attack and with small angle of attack. When there is non-condensing gas in the tail bubble，the connection process between shoulder bubble and tail bubble will be accompanied by the rapid pressure change in the bubbles.
