Seven dicarboxylates of calcium were synthesized. The effect of dicarboxylate on the formation of P-form polypropylene was investigated by X-ray diffraction. Calcium pimelate, calcium suberate, calcium phthalate, and calcium terephthalate have been found to be an effective beta-nucleator. The K-x values of the isotatic propylene samples with 0.5 wt% of the nucleators above are 0.95, 0.96, 0.93, and 0.62, respectively. Calcium succinate, calcium adipate, and calcium sebacate behave invalidly on the nucleating of the beta-phase. We conducted an investigation on the affect of particle shape, crystal form, and crystallinity upon the level of the beta-form. The X-ray diffraction of the effective nucleators reveals a common character that their first reflection locate at the d-spacing between 10 to 13 Angstrom, indicating structural similarity of the nucleators with beta-polypropylene. The nucleation mechanism is explained by the cooperative effect of the nonpolar and polar part of nucleating agents in the crystallization of polypropylene.