The formation law of atmospheric plasma sprayed cast iron coating microstructure with spraying distance and its corrosion resistance in H₂SO₄ and NaCl solution were studied. Cast iron coatings were prepared by atmospheric plasma spraying under different spraying distances. The microstructure of two coatings was observed by a field emission scanning electron microscope. The variation of coating porosity was examined by an image analysis method. The change of bonding between splats within the coatings was analyzed. The corrosion resistance of coatings was tested in 0.5mol/L H₂SO₄ and 3.5% NaCl solution by an electrochemical polarization method, and the variation laws for corrosion resistance performance of two coatings were analyzed. The results showed that both coatings exhibited a typical lamellar structure. Compared with the C1 coating prepared at 70 mm spraying distance, the C2 coating prepared at 100 mm spraying distance had more and larger pores and more nonbonded interlamellar interfaces. The porosity of C1 and C2 coatings was 1.53±0.48% and 3.34±0.79% respectively. Passivation appeared when the coatings were immersed in both solutions. Moreover, C1 coating showed a more positive corrosion potential, a lower corrosion current density, and a higher polarization resistance than C2 coating. In H₂SO₄ solution, the corrosion potential, corrosion current density and polarization resistance of C1 coating was -0.448 V, 5.727×10^-3 A·cm^-2 and 3153.6 Ω·cm² respectively, while those of C2 coating was-0.458 V,  6.537×10^-3 A·cm^-2 and 2663.6 Ω·cm²  respectively. In NaCl solution, the corrosion potential, corrosion current density and the polarization resistance of C1 coating was -1.088 V, 2.553×10^-4 A·cm^-2 and 3584.0 Ω·cm² respectively, while those of C2 was -1.098 V, 6.159×10^-4 A·cm^-2 and 3341.9 Ω·cm² respectively. The lower impact particle and interface temperature led to the higher porosity of C2 coating, hence the number of electrochemical reaction cells in the corrosive medium increased, therefore, the corrosion resistance of C2 coating became poor.