A mobile detection device and a detection method are provided. The mobile detection device (100) includes: a bearing platform (10), being arranged fixedly, and including a bearing surface (11) bearing an object to be detected; a movable gantry (20), located on a side of the bearing surface bearing the object to be detected and configured to be movable relative to the bearing platform (10); a movable bearing device (30), located on a side of the bearing surface (11) away from the movable gantry (20) and configured to be movable relative to the bearing platform (10); a first radiation source (41), arranged on one of the movable gantry (20) and the movable bearing device (30), and a first detector array (51), arranged opposite to the radiation source (41) and arranged on the other of the movable gantry (20) and the movable bearing device (30), wherein the movable gantry (20) and the movable bearing device (30) are configured to be moved synchronously relative to the bearing platform (10).