The invention relates to an apparatus and method for the in-situ real-time observation of submarine sand waves. The apparatus includes an observation system and auxiliary devices. The auxiliary devices comprise an auxiliary ship and a hoisting device; the observation system includes a gravity anchor, a fiber grating floating earth weight sensor, a Kevlar cable, an underwater acoustic releaser group, a lower floating ball bracket, a wave and tide gauge, an upper floating ball bracket, an MRU three-dimensional attitude sensor, a satellite communication machine, an imaging sonar, a solar cell anda main floating body. The principle of the apparatus and the method is characterized in that submarine pressure change caused by the migration of the submarine sand waves is observed, the time interval, elevation and wavelength data of two adjacent extreme submarine pressures are analyzed, and the migration rate of the submarine sand waves is calculated. The method includes the following steps: selection of an observation point and a deployment time, system deployment, recovery, and data processing. The apparatus and the method provide a new idea for the in-situ real-time observation of the submarine sand waves, have the characteristics of simple and easy device, long in-situ real-time measurement period and wide applicable water range, and can realize the in-situ real-time long-term observation of the migration of the submarine sand waves.