The invention belongs to aquaculture machinery, and relates to a horizontal water tilling machine which mainly comprises a motor, reduction gearboxes, an impeller and a floating body. The reduction gearboxes include a primary reduction gearbox and a secondary reduction gearbox, the primary reduction gearbox is integrated with the motor, an output shaft of the primary reduction gearbox drives a bevel pinion, the bevel pinion drives a bevel gear wheel, the bevel gear wheel and a cylindrical pinion are coaxial, the cylindrical pinion drives a cylindrical gear wheel, the output shaft penetrates through a seal, then extends out of one side or two sides of a gearbox body and drives the impeller to rotate, and the integral horizontal water tilling machine floats on a water surface owing to the floating body. The primary reduction gearbox is connected with the secondary reduction gearbox by a flange, and the positioning dimension of a joint surface of the flange is identical to that of a joint surface of a flange of a motor of an aerator. The horizontal water tilling machine has the advantages that the horizontal water tilling machine is applied to aquaculture, when fish and shrimp are young, oxygen consumption is low, the water tilling machine can be started to enable water to flow, the quality of the water of a pond is improved, and the water tilling machine is low in power consumption; and when the fish and shrimp grow to a certain degree, the oxygen consumption is increased, the pond can be aerated as needed by means of disassembling the primary reduction gearbox and using the horizontal water tilling machine with the motor of the aerator, and other structural change is omitted.