The effects of the additional resistance in a circuit under constant voltage on characteristics of microarc oxidation (MAO) coatings of pure titanium substrates in Na2SiO3-Na3PO4 solution were studied. The results show that the coatings’ growth characteristics, phase component, surface morphology and the samples’ corrosion resistance after treatment are strongly influenced by the additional resistance in the MAO process. The phase component and surface morphology of the coatings prepared without the resistance are closely relative to the treating voltages; when the voltage is lower than 450 V, the coatings consist of anatase phase; when the voltage is greater than or equal to 450 V, the coatings consist of anatase and rutile phases. While the phase component and surface morphology of the coatings prepared with the resistance have little relation with the treating voltage; the coatings only consist of anatase phase, and the micropore size is smaller whose distribution is more uniform. The corrosion resistance test in sulfuric acid solution (30%) shows that the corrosion resistance of the samples prepared with the resistance is 40% higher than that prepared without the resistance averagely