Composites of polyaniline with calcium carbonate particles (PANI/CaCO3) with different CaCO3 content (0-40 %w/w) were prepared. Two different methods of in situ polymerization and solution mixing were used for PANI/CaCO3 composite preparation. The composite was characterized using FT-IR, SEM, electrical conductivity measurement and cyclic voltammetry techniques. The incorporation of CaCO3 particles in polyaniline matrix in both methods of composite preparation was confirmed by FTIR results. Electrical conductivity measurements showed that the conductivity of the composite decreases by increasing the CaCO3 loading in polyaniline. Also, the anticorrosive property of the PANI/CaCO3 composite coating on iron samples was investigated in various corrosive environments. According to the results, the corrosion rate or corrosion current of PANI/CaCO3 composite coated iron coupons was much lower (96.75%) than polyaniline coated samples. Also, results showed that the corrosion current of composite coated samples varies with the variation of the CaCO3 content in composite coating, and the optimum CaCO3 content of composite coating to achieve the best anticorrosive performance on iron is 10 %w/w.