In this study, 1 wt% of nucleating agent LAK-301 was introduced into poly (lactic acid) (PLA) to enhance the heat resistance of PLA materials through the nucleation effect and thermal processing. The changes in thermal, mechanical, and dielectric properties of PLA materials before and after thermal modification were also investigated. Thermal load deflection temperature experiments showed that P/L-60s increased the HDT to 146.18 ℃. Differential scanning calorimetry showed that the crystallinity of P/L-60s was increased by 92.6% compared with pure PLA, and X-ray diffraction experiments showed that LAK-301 could increase the growth rate of crystal cells. The results of impact strength tests illustrate that P/L-60s can elevate the impact strength by 54.32%. The results of scanning electron microscopy revealed that the fracture surface of P/L composites is rougher, which corresponds to the enhancement of impact strength after crystallization. The dielectric property tests show that LAK-301 decreases the dielectric loss of P/L composites. The above studies show that the addition of nucleating agent LAK-301 in combination with thermal processing can significantly enhance the heat resistance and toughness of PLA, and this solution can broaden the scope of application of PLA in power equipment.