Abstract: Ultrasonic annular array water spray testing system was applied to detect electron beam welded defects of major aviation titanium alloy weld assembly.Based on the system,water jet was designed for ultrasonic annular array probe.According to probe sound field curve calculated by CIVA-software,lumen diameter and lumen shape were discussed in order to obtain designing parameter of water jet.Afterwards four types of water jet were designed for the experiment.In view of the experiment it was concluded that the water jet lumen curve should contain probe sound field curve,lumen diameter had greater effect on detection than the lumen shape and adopting vertical wall cylinder water jet could achieve the best effect of detection.In the end,field test verified that using vertical wall cylinder water jet could achieve high sensitivity and meet the needs of the field test.