The present invention discloses a cordless electromagnetic induction system, which comprises a cordless pen and a tablet connecting to a host. In this regards, the cordless pen comprises a battery for supplying power to the cordless pen, a radio frequency (RF) oscillation circuit for generating RF signal representing the location and status of the cordless pen, a wake up apparatus, and a sleep control apparatus. The wake up apparatus sets the cordless pen into a working mode and startup the RF oscillation circuit when receiving a wakeup RF signal. Moreover, the sleep control apparatus sets the cordless pen into a sleep mode and shutdown the RF oscillation circuit when the cordless pen is idle for a while in the working mode. In this embodiment, the tablet comprises a control apparatus, a tablet RF emitter, and a tablet RF receiver for receiving RF signal, representing the location and status of said cordless pen, from the RF oscillation circuit and informing the control apparatus. In this regards, the control apparatus starts up the tablet RF emitter when no RF signal from the RF oscillation circuit received, and shuts down the tablet RF emitter when RF signal from the RF oscillation circuit received.