Abstract: Lanthanum p-methyl benzoate (LPB) was synthesized by using lanthanum chloride, p-Toluic acid and sodium hydroxide as raw materials, and the resultant product was characterized by means of elemental analysis and FTIR. The effect of LPB on the thermal stability and discoloration of polyvinyl chloride (PVC) were investigated by Congo red experiment and high-temperature hot aging tests. Moreover, a comparative study was carried out for LPB with other stabilizers such as zinc stearate, calcium stearete, lanthanum stearate and pentaerythrotol, and LPB was also mixed with other stabilizers to form a complex stabilizer. The results indicated that the thermal stabilizing effect on PVC is not good enough when LPB was used alone, which also resulted in poor long-term stability and anti-discoloration performance. When the mass ratio of LPB/calcium zinc composite/pentaerythrotol mixture was set to 2/1/2 and its total dosage was determined as 4 wt % of PVC, the stability time of PVC reached 48 min. The stable mechanism of LPB could be ascribed to the absorption of the HCl released by the decomposition of PVC. Such absorption could result in the production of LaCl3 and therefore reduced the catalytic effect of HCl on the degradation of PVC and inhibited the degradation of PVC accordingly.