Foreign matter detection method and device, and wireless charging control method and device

The invention discloses a foreign matter detection method and a device, and a wireless charging control method and a device. The foreign matter detection method comprises steps that, the present first switch frequency of a wireless charging system is detected when primary and secondary sides of the wireless charging system are utilized for wireless charging; the second switch frequency of the wireless charging system is acquired on the condition that no foreign matter exists between the primary side and the secondary side of the wireless charging system; if the difference of the first switch frequency and the second switch frequency is in a preset scope, the primary side and the secondary side of the wireless charging system are determined to have foreign matter. The foreign matter detection method can effectively detect whether foreign matter exists between the primary side and the secondary side of the wireless charging system.