Abstract: Lanthanum diitaconate dibutyltin was synthesized with dibutyltin oxide, maleic acid and lanthanum nitrate as raw material, and its structure was characterized by Fourier-transform infrared spectroscopy and elemental analysis. The thermal stability of lanthanum diitaconate dibutyltin used for PVC was studied by means of thermal aging oven method, Congo red testing method, torque rheometer and ultraviolet spectrometer. The synergistic effects of lanthanum diitaconate dibutyltin with pentaerythritol and calcium/zinc stearate were discussed respectively. The results indicated that lanthanum diitaconate dibutyltin had a good thermal stability when added into PVC alone, which could significantly depress the rapid generation of long chain polyene structure in PVC and retarded the thermal degradation of PVC. The combination of lanthanum diitaconate dibutyltin and pentaerythritol could increase the static thermal stability time of PVC and delay the change in initial color. The combination of lanthanum diitaconate dibutyltin and calcium/zinc stearate could reduce processing energy consumption and enhance the stretching and impact properties of PVC.