The present invention relates to underwater communication and, more particularly to a signal transmission method and device which configure and transmit physical channel information such that low-power control is performed in underwater communication. The present invention configures the physical channel information such that a reception node side can check through a combination of preambles whether a signal is provided to itself, when forward direction communication is performed in a centralized underwater communication network. Therefore, the present invention performs the control such that only a relevant reception node requiring data reception performs a demodulation operation, without requiring all reception nodes to always perform demodulation in a forward direction communication process. Through this process, many reception nodes do not perform unnecessary demodulation operations in the forward direction communication process, thereby providing an effect of preventing unnecessary power consumption.