In this article, the influence of alkaline earth dehydroabietates, which were prepared from Na-dehydroabietate, on crystallization of polypropylene (PP) from the melt state was studied by differential scanning calorimetry and polarization microscopy. It was found that magnesium dehydroabietate could improve mechanical properties and crystallization temperatures of PP and also decrease the size of spherulites. Kinetic analysis of PP isothermal crystallization showed that magnesium dehydroabietate decreased the fold surface energy of the developing crystals of PP and promoted the nucleation and crystallization of PP. However, calcium dehydroabietate increased the fold surface energy of the developing crystals of PP, but had no nucleation effect oil PP.