The invention discloses a thoracic constant pressure loading device comprising a driving mechanism, a lifting mechanism and a force applying mechanism, wherein the driving mechanism comprises a stepping motor, a first bevel gear shaft and a second bevel gear shaft which are arranged in the same horizontal shaft direction and are sequentially connected through a shaft connecting piece; the liftingmechanism comprises two same lifting devices, wherein each lifting device comprises a bevel gear, a lifting shaft, a nut and a supporting member which are sequentially connected from bottom to top; the bevel gears of the two lifting devices are meshed with the first bevel gear shaft and the second bevel gear shaft which form an axial intersection angle of 90 degrees respectively; an upper sectionof each lifting shaft is processed into a screw section, the nut is connected to the screw section to form a screw structure, a lower section is fixed in a central hole of the bevel gear, the supporting member is fixed on the top of the nut; the force applying mechanism is arranged on the lifting mechanism, and the lifting mechanism drives the force applying mechanism to lift and transfer constantpressure; the thoracic constant pressure loading device can accurately control the feeding amount of the force applying mechanism, the continuous constant force loading is achieved, a large torque can be sustained, the transmission is reliable and the lifting is stable.