The invention mainly discloses a stirring device and method for stirring sea mud. According to the technical scheme, the stirring device comprises a chassis, a first motor, a second motor, a stirring machine head and a conveying device; the stirring machine head comprises an outer drill pipe, an inner drill pipe, first stirring blades and second stirring blades; the inner drill pipe is provided with a drill bit and third stirring blades; the drill bit is located at the bottom end of the inner drill pipe, and the third stirring blades are located between the first stirring blades and the second stirring blades; the inner drill pipe is provided with a first conveying channel and two first discharging sections; and the third stirring blades are provided with a second conveying channel and a second discharging section. The method comprises the steps of primary stone crushing, grout spraying, stirring and sinking, in-situ stirring, detecting, grout spraying, stirring and ascending, secondary detecting and stirring machine head cleaning. According to the stirring device and method, the multiple stirring blades are adopted, stirring is uniform, and the stirring efficiency and the stirring mixing effect are improved; and the multiple discharging sections are arranged, the one-time grout spraying amount is large, the pile forming speed is high, the pile forming quality is good, and the construction cost is saved.