Toward　the　problem　of　the　metal　material　early　degradation　of　mechanical　properties,　this　research　developed　a　robust　experimental　procedure.　Using　this　system,　ultrasonic　nonlinearity　parameters　of　AZ31magnesium　monotonic　load　and　fatigue　samples　were　measured.　The　experimental　results　show　that　there　is　a　significant　increase　in　β　linked　to　magnesium　mechanical　performance　degradation,　into　plastic　deformation　stage　and　before　the　fatigue　life　of　55%.　Monotonic　load　sample　was　observed　by　optical　microscopy　in　the　same　place,　dislocation　slip　bands　increase　with　stress.　Macro-mechanics,　nonlinear　ultrasonic　testing　and　microscopic　observation　results　show　that　ultrasonic　nonlinearity　parameters　as　a　bridge　between　micro　and　macro　can　characterize　the　mechanical　properties　of　early　degradation.　However,　in　the　context　of　low-cycle　fatigue,　changes　of　loading　stress　and　the　fatigue　model　with　tension-tension　fatigue　and　tension-compression　fatigue　had　no　significant　effect　to　the　experimental　results.