The invention provides a method and device for measuring the elasticity of hardened cement for cementing of oil-gas wells. The measurement method comprises: determining the loading and unloading rates of the hardened cement; determining the maximum loading on the hardened cement; determining the experimental temperature and the experimental pressure of the hardened cement; establishing a stress-strain curve for the hardened cement; and describing the elasticity of the hardened cement with the degree of strain recovery of the hardened cement in different cycles, and describing the mechanic integrity of the hardened cement with the degree of damage to the hardened cement in different cycles. The invention further provides a device for measuring the elasticity of hardened cement for cementing of oil-gas wells. The measurement method and device of the present invention provide a universal comparing platform for research on hardened cement modification as well as examination of domestic and foreign special cement slurry systems, which is of great significance in evaluation of well hole integrity and well life.