Abstract: The phase component and content percentage of rebar corrosion products in concrete with different corrosion approaches are different,so the volume expansion multiple and corroded expansion effects of rebar corrosion products are also different.The phase component and content percentage of corrosion products in different chloride corroding ways (invaded by chloride and mixed into chloride),different corroding extents (before and after cracking) and different test conditions (artificial accelerated climate environments,natural condition and the Galvanostatic Method) were investigated with the application of the X-ray diffraction analysis technique,and the computing method of volume expansion multiple of rebar rust was presented in the paper.The research indicates that the content percentage of each corrosion product in various chloride corroding ways is different.and corrosion products under natural condition and artificial accelerated climate environments are more sufficiently oxidized than those by the Galvanostatic Method.The volume expansion multiple of rebar corrosion products with different corrosion approaches is close to each other,about 2.20-2.45.But the volume expansion multiple by the Galvanostatic Method is a little less than those under artificial accelerated climate environments and natural condition.The climate environment condition has no distinct influence on the volume expansion multiple of rebar corrosion products.