The invention discloses a metal material deformation amount test box and a detection method thereof. The metal material deformation amount test box comprises a box body (1), a tray (4), a sensor assembly (2), a temperature regulating device (6) and a central processor, wherein the tray (4) is used for accommodating and positioning a plurality of metal U-shaped pieces (3), the sensor assembly (2) is used for detecting the deformation amount of each metal U-shaped piece (3), and the temperature regulating device (6) is used for carrying out a temperature raising operation and a temperature reducing operation on the temperature inside the box body (1). According to the invention, the metal material deformation amount test box not only can be used for measuring the thermal deformation amount of a product when the temperature rises, but also can be used in a low temperature environment. Therefore, the metal material deformation amount test box is more accurate in test for the material deformation amount of the metal U-shaped pieces.