Mechanism of sulfate attack is a very complicated process. In the laboratory, there are a variety of testing methods for cement resistance to sulfate attack. But there are still some problems. For example, the method often used in the United States Association standards and testing (ASTM) does indicate that expansion happens in the event of specimens’ breakage, but not point clearly the minimum amount of expansion leading to the strength damaged. In the present study, the method of measuring expansion of hardened cement paste sulfate resistance is discussed. It is found that experimental measurements can be used to study the erosion of sodium sulfate solution, but not be used to evaluate the anti-corrosion properties of hardened cement paste to magnesium sulfate.