The disclosed provides a machine of paste shrinkage and expansion for timely monitoring a paste shrinkage in a Z direction during a UV curing process and for obtaining a change rate of a paste in a Z direction after a certain process. The machine comprises: a bottom substrate; a top substrate which is transparent and configured to be placed on the paste so that the paste is sandwiched between a top surface of the bottom substrate and a bottom surface of the top substrate, wherein the top surface of the bottom substrate and the bottom surface of the top substrate are provided with first and second reflecting layers, respectively, and define a thickness of the paste; a platform for supporting the bottom substrate; a plurality of pressing clamps configured for securing the bottom substrate on the platform in the Z direction; a plurality of pushing clamps configured for securing the bottom substrate in radial and circumferential directions; a plurality of UV sources positioned uniformly around the paste; and a sensor configured for measuring the thickness of the paste. The bottom substrate and the platform comprise a substrate dial and a platform dial, respectively, and the bottom substrate has a profile consistent with the platform dial. The disclosed provides methods for timely monitoring a paste shrinkage in a Z direction during a UV curing process and for obtaining a change rate of a paste in a Z direction after a certain process.