The thermal stability of the heterogeneous nucleation effect of polypropylene (PP) nucleated with an organic phosphate (A) and two kinds of sorbitol derivatives (B and D) was investigated by DSC multiscanning. For pure PP, the peak temperature of crystallization (T-c(p)) was little changed with an increasing number of DSC scans, indicating that nucleation of PP is thermally stable. For the PP nucleated with an organic phosphate (PPA), the temperatures at the onset of crystallization (T-c(on)) and at the completion of crystallization (T-c(f)); the peak temperature of crystallization (T-c(p)) and melting (T-m(p)); and the heat of crystallization (DeltaH(c)) and fusion (DeltaH(m)) of PP are higher than those of pure PP and were little influenced with an increasing number of DSC scans. For PP nucleated with the sorbitol derivatives (PPB and PPD), the T-c(on), T-c(p), T-c(f), and T-m(p) decreased with an increasing the number of scans. These results indicated that the thermal stability of heterogeneous nucleation effect of the nucleating agent A is higher than that of nucleating agents B and D.