The invention provides a mobile robot and a charging system and charging method thereof. The mobile robot comprises a controller, and also comprises an electrical quantity monitoring device, a mobile drive device, a signal strength monitoring device, a radio receiving device, a wireless charging module and an electric energy storage module which are all connected with the controller. The charging control method comprises the steps that the controller sends a remnant electrical quantity acquisition instruction to the electrical quantity monitoring device when receiving a motion instruction from a user; when the electrical quantity is small, the controller sends a current position radio signal strength acquisition instruction to the signal strength monitoring device, the radio signal strength variation rate is calculated, and the moving parameters of the mobile drive device are set according to the obtained radio signal strength variation rate; and when the obtained radio signal strength variation rate meets the set variation threshold value, an operating instruction is sent to the radio charging module. By adoption of the wireless charging mode, precise positioning and charging port inserting are not needed, abrasion of charging equipment can be avoided, the service lives of a charger and the charging port of the mobile robot are prolonged.