Abstract: T tubular joints were used in the fatigue contrast tests of low carbon steel and austenite stainless steel 1Cr18Ni9Ti in two conditions:welded and treated by ultrasonic peening.The aim is for fatigue design problem research of tubular joints treated by ultrasonic peening.Test results indicate that:(1) If attributed by hot spot stress,10 is more appropriate for the rate of slope m of the corresponding fatigue design S-N curve as for the tubular joints treated by ultrasonic peening before loading,while 3 is more appropriate for it as for the tubular joints treated by ultrasonic peening after loading.(2) Under the stress ratio R=0,the corresponding fatigue design S-N curve(attributed by hot spot stress,m=10) of low carbon steel and austenite stainless steel 1Cr18Ni9Ti tubular joints treated by ultrasonic peening before loading is lgN=30.78-10lgS.(3) Under the stress ratio R=0.5,the corresponding fatigue design S-N curve(attributed by hot spot stress,m=10) of low carbon steel tubular joints treated by ultrasonic peening before and under loading are lgN=28.0-10lgS and lgN=13.37-3lgS respectively.