The invention relates to a measuring device and measuring method for well-cementing annular weight loss of cement slurry. The device is mainly composed of a base, a control panel, an upright strut, a slurry cylinder and a computer, wherein the upright strut is connected with the slurry cylinder through a support shaft and with the control panel through a rotating shaft; the slurry cylinder is provided with a pressurizing hole, an inner cylinder, an outer cylinder and an annular space between the inner and outer cylinders; the slurry cylinder is a segmented combination with each segment provided with a temperature sensor, a pressure sensor and a heating cooling jacket; the slurry cylinder controls the eccentricity of the inner cylinder through an eccentric cover, three pressure sensors arearranged at the lower part of the slurry cylinder; and the temperature sensors and the pressure sensors respectively transmit data to the computer. The invention can simulate different temperature differences of downhole temperature changing along with hole depth, and acquisition and regulation are controlled by the computer, so that the operation is simple and convenient; the eccentricity of thesleeve is controlled by the eccentric cover, so that the safety, stability and reliability are ensured; and the measuring device and the measuring method are suitable for operations such as petroleumand natural gas well cementation, cement extrusion, cement injection and the like.