The present disclosure provides an adapter, a multi-device detection system and a detection method. The adapter includes a circuit board, a male connector, a first female connector and a second female connector arranged on the circuit board. The male connector is electrically connected to the first female connector and the second female connector. The male connector is provided with two independent D+ pins and two independent D− pins. One of the two independent D+ pins is electrically connected to a D+ pin of the first female connector, and the other one of the two independent D+ pins is electrically connected to a D+ pin of the second female connector. One of the two independent D− pins is electrically connected to a D− pin of the first female connector, and the other one of the two independent D− pins is electrically connected to a D− pin of the second female connector. The present disclosure further provides a multi-device detection system and a detection method thereof.