A method and device for determining a time of arrival (TOA), a terminal device, and a non-transitory computer-readable storage medium are disclosed. The method may include: determining a detection start time on a correlation waveform based on a leading edge detection threshold; determining a noise threshold on the correlation waveform, and determining a quasi-TOA according to the detection start time; and determining the TOA according to data information in a target area of the correlation waveform and the noise threshold, where the target area is determined based on the quasi-TOA and a detection length.