Abstract: The present invention discloses a domain wall straightening method of a periodically poled ferroelectric crystal. In the present invention, by testing a piezoelectric coefficient of a poled sample, the poling condition of the sample can be judged nondestructively, and the region of uniform poling can be screened out. At the same time, according to the calculation result of a duty cycle, the continuation or stop of poling, and the re-poling after single domain can be judged. The flatness of the domain wall is judged through the change quantity of the piezoelectric coefficient, and the size and the duration of the poling voltage are adjusted in time, to accurate control the poling process, so as to obtain high-quality periodically poled crystals.