Abstract: Oedometer tests have been carried out to study the change rules of the compression modulus values in different corrosion products. The rust samples were divided into four groups (0.01~0.05 mm， 0.05~0.08 mm， 0.08~0.10 mm and 0.10~0.32 mm) by the cement fineness negative pressure sieve analyzer. The equivalent diameter of each group could be obtained through KH-7700 3D video microscopy system respectively. The oedometer tests of the rust samples of four particle size ranges have been made and analyzed respectively. Analysis results show that the compression modulus of the reinforcement corrosion products is not a constant value， but is increasing linearly with the increase of the compressive stress. The compression modulus of the reinforcement corrosion products of similar average particle size is related to its chemical composition under the same stress level. The rangeability of the compression modulus value would be smaller with the increase of the compressive stress when the corrosion products are more fully oxidized. Assuming that the reinforcement corrosion products are of elastic materials and their poisson′s ratio is 0.25， the elastic modulus values are between 0.017 GPa and 0.733 GPa when the concrete cover gets cracking due to the steel bar corrosion expansion, which can provide references for selecting analysis parameters in studies of concrete cracking induced by reinforcement corrosion.