The invention discloses a marine air gun three-dimensional sub-array delay exciting method. Hanging points of air guns in a sub-array are provided with at least two different sinking depths, and the air guns at the positions of the hanging points at the different sinking depths form the three-dimensional sub-array. Exciting time of the air guns at the different sinking depths is different. By the adoption of the method, when a receiving method is determined, the three-dimensional sub-array can obtain low-frequency, sufficient and wide-frequency-band seismic data through the method of changing seismic exciting methods, the requirements for original quality of the seismic data from shallow zone exploration, medium zone exploration and deep zone exploration are met, and exploration cost is saved.