Provided are a copper-containing, high-toughness and rapidly degradable magnesium alloy, a preparation method therefor and the use thereof, wherein same relate to the field of materials for oil and gas exploitation. When the magnesium alloy is in an as-cast state, an extrusion state or an aging state, a strengthening phase thereof mainly includes an Mg12CuRE-type long-period phase and an Mg5RE phase and an Mg2Cu phase, the Mg12CuRE-type long-period phase has a volume fraction of 3-60%, the Mg5RE phase has a volume fraction of 0.5-20%, and the Mg2Cu phase has a volume fraction of 0.5-15%, wherein RE is a rare-earth metal element.