Abstract: Addressing the problem that in case of the ultrasonic testing,using the pure transverse wave can not at the same time perform detecting longitudinal flaws on both inner and outer surfaces of the heavy-wall seamless steel pipe,permissible range of the UT incidence angle is calculated,and the seamless steel pipe t/D ranges as detected by the pure transverse wave and the deformed transverse wave are theoretically analyzed,and also the wall thickness range of seamless steel pipes with regular O.D.as detected with the pure transverse wave and the deformed transverse wave is presented.Based on the analysis result,it is concluded that for pipes with t/D ≤ 0.20,the pure transverse wave should be used for detecting both inner and outer surface flaws,and for pipes with 0.20 ∧t/D ≤ 0.26,the deformed transverse wave should be used for surface detection so as to realize detection of longitudinal inner surface flaw of the heavy-wall seamless steel pipe.