Abstract: This paper describes a series of tests carried out on the uniaxial compression of ex isting un-carbonated concrete that had been in service for 10, 20 and 40 years, respectively, and 24 complete stress-strain curves in total were obtained.Compared with fresh concrete of the same strength ( 28 days of curing period), the behavior parameters in terms of ductility ratio, peak strain, ultimate strain and elastic modulus were found to decline to different degrees and the chang ing laws of these parameters with the increase of service life were generalized based on the test results. It is therefore recommended that the adverse effects of these parameters should be taken into account if members are planned to be used further.