The invention provides a device and a method for testing the bond-slip performance of new concrete and old concrete. The device comprises a test piece fixing device, a loading device and a data acquisition unit, wherein the test piece fixing device comprises a bottom plate, a ground anchor bolt, a baffle and a locating bracket, and is used for fixing a new concrete and old concrete bonding test piece during a test and ensuring that the test piece does not move; the loading device comprises a loading end plate and a hydraulic jack and is used for applying thrust onto the new concrete in the new concrete and old concrete bonding test piece so as to enable the new concrete and the old concrete to move alternately and generate shear stress on the bonding surface; the data acquisition unit comprises a dial indicator, a force sensor, a data acquisition system and a central control computer. The push-out shear testing device is adopted, the instrument is simple in operation, a complete shear stress-slippage curve of the two ends of the bonding test piece can be obtained, and the bond-slip relationship of all points along the bonding length direction can be obtained, so that the device and the method are widely used in the study of new concrete and old concrete bonding performance.