Electronically controlled liquid-crystal gratings have advantages such as small volume and agile optical beam steering in satellite laser communication and laser radar. However, the key issue for performance evaluation of liquid-crystal gratings is to obtain the modulated beam wavefront by it. Conjugation phase shifting interferometry measuring liquid-crystal gratings wavefront is presented. In the experiment, the measured far-field intensity is in accordance with the theoretic analysis on near-field wavefront. This technology shows a new beam steering control method with near-field wavefront measurement.