Embodiments of the present invention provide a sensing threshold determining method and a sensor node device. The sensing threshold determining method includes: measuring, by a sensor node, a target frequency band and determining used frequencies in the target frequency band and received signal strength of the sensor node at the used frequencies, where the used frequencies in the target frequency band include frequencies being used or having been used by a primary user transmitter in the target frequency band; and determining, by the sensor node, a sensing threshold for unused frequencies in the target frequency band according to the received signal strength at the used frequencies, where the unused frequencies include frequencies that are not used by the primary user transmitter in the target frequency band. With the embodiments of the present invention, a sensor node can determine a proper sensing threshold for unused frequencies.