The invention discloses an early drowning detection method and system, and the method includes the steps: wearing a signal transmitter on the head of a wader to enable the signal transmitter to enterand leave the water surface with the mouth and nose of the wader; enabling the signal transmitter to periodically transmit a radio frequency signal when the signal transmitter is located on the watersurface or under the water surface; enabling a processing device to receive the radio frequency signal, calculating the cumulative transmission duration of the radio frequency signal in a current timeperiod, and determining the respiratory resistance of the wader by using the ratio of the cumulative transmission duration to the current time period, and performing the comparison with a set threshold for determining whether the wader is drowning or not. The system includes the above signal transmitter and the above processing device. The method achieves the quantification of the degree of respiratory resistance of the wader objectively, accurately and in real time by counting the cumulative emission duration of the signal transmitter worn by the wader in the current time period, so that thewader can be timely discovered when the wader appears.