Abstract: The body, channel and the sealing surface of valve in Christmas tree are susceptible of corrosion under the condition of high temperatures, high pressures and corrosive medium. The qualitative and quantitative analysis of the corrosion defects was studied using the A scanning, B scanning, C scanning and S scanning of ultrasonic phased array. The results show that the minimum wall thickness of body and channel of valve could be measured by using the C scanning of ultrasonic phased array.S scanning and C scanning of ultrasonic phased array can be used to detect the sealing surface of valve.