A portable electronic device with a movable door cover including a host, at least one door cover pivoted to the host to be opened or closed relative to the host, at least one linking member connected to the door cover, a shape-memory alloy (SMA) spring connected between the linking member and the host, and a heat source disposed in the host is provided. The SMA spring is affected by heat generated from the heat source to form at least two stretching states, and drives the door cover through the linking member to form at least two states including said being opened or closed.