Abstract: The ultrasonic P-wave tests on frozen remolded loess under uniaxial loading are conducted by using RSM-SY5(T) nonmetal ultrasonic test meter to study the velocity characters of P-wave. The characteristics of acoustic waveforms and wave frequency spectra of frozen remolded loess are investigated by using the short-time Fourier transform and wavelet transform. The experimental results indicate that the P-wave velocity is affected by the temperature and external loads, and the velocity decreases with the increase of temperature and generally increases at first and then decreases with strain during the loading process. There is an exponential relationship between the uniaxial compressive strength and the initial P-wave velocity, and the correlation between them is very good. With the increase of external loading, the shape of spectral curve will change and the spectral area and main frequency will decrease. The coda waves are not developed at the initiation of loading and gradually develop with the increase of stress and the emergence of cracks. The characteristic parameters of acoustic waves can reflect the development of internal cracks of frozen remolded loess during loading to some extent.