Abstract: In this work the effects of solution temperature on microstructure and ultrasonic response of nickel-based super alloy GH4169 were examined. Characteristic parameters of grain size and shape were measured. Longitudinal wave echo method and collinear penetration method were used to test the samples, and the ultrasonic parameters, such as velocity, attenuation coefficient, and relative nonlinear coefficient, were calculated. The power and waveform index of intrinsic mode functions (IMFs) of backscattered signals dealt with empirical mode decomposition were calculated. Comparison between ultrasonic and microstructure data shows that the attenuation coefficient, velocity, and nonlinear coefficient could be used to make an effective identification of phase transition. The attenuation coefficient increased with the increase of grain size and was strongly sensitive to the change of grain size. Both power and waveform index of IMFs of backscattered signals could be used to estimate grain size, but they were difficult to characterize the axial ratio of grain.