Abstract: As the cold end life-limited part of aero-engine, the internal residual stress of titanium alloy discs is one of the key factors affecting the failure probability during service. In order to study the internal residual stress of the titanium alloy disc and the accuracy of testing methods, an isothermal forging TC4 special titanium alloy disc was designed. After quenching, the internal residual stress the disc was sequentially tested by the ultrasonic method, deep hole drilling method and contour method. The residual stress distribution patterns within the disc tested by the three methods were compared and analyzed. The results show that the maximum tensile residual stress in the center of the isothermal forging TC4 special disc after quenching can reach 47 MPa. The contour method can obtain a two-dimensional circumferential residual stress cloud of the meridional section of the disc, demonstrating good stability and accuracy. The deep hole drilling method exhibits greater dispersion and edge effects, with a maximum difference from the contour method of 20-30 MPa. The ultrasonic method can comprehensively reflect the integral residual stress of the disc through the range of velocity, but is significantly affected by the rim of the disc, with a maximum error of up to 36.9% compared to the contour method. After eliminating the edge effects, the ultrasonic method can better reflect the circumferential residual stress distribution of the disc, with a maximum error of only 6.5% compared to the contour method.