The invention proposes a detection method and device for an SIM card, and a terminal. The method comprises the steps: detecting a placement mode of the SIM card through a detection switch; switching a data line of the SIM card to a data channel according to the placement mode; and carrying out the data exchange through a data channel. The method solves a problem that the SIM card is burnt out or cannot be recognized because the SIM card is inserted reversely, removes the anti-fool design of a cassette, achieves the intelligent detection of the SIM card through a circuit design device, enables the card replacement to be convenient and quick, enables the insertion operation to be very free, and meets the requirements of user experience.