Abstract: Analyzed here in the article are the factors as affecting the result of the ultrasonic detection to the seamless Ti alloy steel pipe.It is regarded via the analysis that the internal surface rolling groove defect of the said pipe obviously affects the result of ultrasonic detection as taken to it;such defect leads problems i.e., high noise wave level, lowering the sensitivity margin, unrecognizing between the noise wave and the defect wave, and increase of the false alarm rate, and even causes the ultrasonic detection system not to work;the effects by the equiaxed microstructure and the duplex microstructure of the said pipe as heat treated on the ultrasonic detection result are relatively slightly, whereas the asrolled lamellar microstructure causes relatively higher noise wave level, and rather obvious acoustic energy attenuation.