A long term immersion test of mortar in sulfuric acid is carried out to investigate the effects of fly ash (FA) and silica fume (SF) on anti-corrosion characteristics. The mortar specimens have water to binder ratios (W/B) ranging from 0.5 to 0.7 and are divided into two series. Series one uses admixture of FA with replacement ratio from 0~0.3 and series two uses admixture of SF with replacement ratio from 0~0.1. The specimens are soaked in sulfuric acid with a pH value of 3.50 for 150 days. The portable pH meter is used to monitor the pH changing of the soak solution. The titrating sulfuric acid with concentration of 0.125mol/l is added to maintain the original pH value of the solution and then sulfuric acid consumption of specimens is recorded. A partial correlation analysis of experiment results shows that the effects of FA and SF on mortar resistance to sulfuric acid would change with the water binder ratio.