The invention relates to a method and system for labeling the type of electroencephalographic signal data in a sleep state. The method includes the steps that wavelet decomposition is carried out on an electroencephalographic signal sample, an electroencephalographic signal is reconstructed according to a preset wavelet coefficient in a low-frequency stage, and a low-frequency electroencephalographic signal is obtained; brain waves are extracted from the reconstructed low-frequency electroencephalographic signal; K synthetic waves and delta waves are detected from the brain waves according to the waveform characteristics of the K synthetic waves and the delta waves; the number of the detected K synthetic waves and delta waves is calculated, and when the number exceeds a preset number threshold value, the signal type of the electroencephalographic signal sample is labeled as sleep. By labeling the type of the electroencephalographic signal sample according to the technical scheme, interference elements mixed into the electroencephalographic signal sample can be eliminated, so that a personal classifier trained with the labeled electroencephalographic signal sample is higher in recognition accuracy rate, and the reliability of the detection result of the personal sleep state detected in a later stage is improved.