The present disclosure provides a device and a method for preparing olefins by methanol and/or dimethyl ether. The device for preparing olefins by methanol and/or dimethyl ether includes: a reactor, including a reaction area and an isolation area from the bottom up and further including a product gas outlet; a guide hood provided in the isolation area; a regenerator, including a regeneration flue gas outlet; a reactor three-stage cyclone separator, including a product gas inlet and a spent catalyst fine powder outlet; a regenerator three-stage cyclone separator, including a regeneration flue gas inlet and a regenerated catalyst fine powder outlet; the regenerator further includes a spent catalyst fine powder inlet and the spent catalyst fine powder inlet is connected with the spent catalyst fine powder outlet by a spent catalyst fine powder transmission pipeline; the device for preparing olefins by methanol and/or dimethyl ether further includes a bubble breaking unit; the bubble breaking unit is provided in the reaction area and a plurality of breaking holes are provided on the bubble breaking unit. The present disclosure solves the problems of low selectivity of light olefins, loss of a catalyst and high consumption of the catalyst.