Abstract: Surface acoustic wave testing was proposed for fatigue crack in aircraft hydraulic pipe. According to the crack morphology and the structural characteristics of pipe head, reference samples and four-channel surface wave focusing probes of 7. 5 MHz were designed and manufactured. After matching special fixture and four-channel instrument with high signal-to-noise, the root defect of smooth nozzle with length of 3 mm and depth of 0. 1 mm, and the root defect of bell mouth with length of 3 mm and depth of 0. 14 mm can be well detected. This method solves the interference of hydraulic oil, assembly and shielding in the pipe, realizes the purpose of convenient operation and reliable detection results, satisfies the requirements of in-service testing, which can provide reference for testing of the same type of thin-walled pipes.