Abstract: Theoretical and experimental studies was carried out on the reference sensitivity and evaluation difference of DL/T 820.2—2019 and NB/T 47013.3—2023 ultrasonic oblique probe detection standards due to the use of different test blocks. By the theoretical calculation and verification, the echo sound pressure difference between the long horizontal hole of ϕ3 mm×40 mm and the long horizontal hole of ϕ2 mm×60 mm was adopted in the two standards, and then the distance-amplitude curve was drawn and analyzed. Finally, the evaluated differences of the two standards were summarized.