In this paper, we propose a femtosecond laser-induced surface periodic structure (LIPSS) based on relaxed ferroelectric PMN-PT crystals. By changing the applied laser parameters, the period of the LIPSS structure is varied from 750 nm to 3 μm. Finally, the phase transition properties of the LIPSS structure are investigated by increasing the temperature. Compared to the phase transition properties of the substrate, the Curie temperature of the LIPSS structure is significantly reduced, and this will provide a possible new idea for the preparation of temperature-controlled modulators based on PMN-PT crystals.