The invention relates to a lathe static stiffness measurement device, which comprises a loading device, a stiffness instrument, a simulation cutter, a load measurement device, a displacement variation amount measurement device and a data processing module. The loading device is arranged on the stiffness instrument, and carries out loading on the simulation cutter; the load measurement device comprises a dynamometer, a three-directional force amplifier and an analog-to-digital converter, wherein the dynamometer is arranged on the simulation cutter and is connected with the three-directional force amplifier, and the three-directional force amplifier is connected with the data processing module through the analog-to-digital converter; the displacement variation amount measurement device comprises displacement sensors, wherein the displacement sensors are arranged at the places of a lathe head, a cutter rest and a tail base respectively; the displacement variation amount measurement device is connected with the data processing module; and the data processing module calculates and displays a static stiffness value and a static stiffness curve. Displacement variation amount at different positions under different loads are measured through the load measurement device and the displacement variation amount measurement device, and thus lathe static stiffness measurement is realized under the effect of different working conditions.