The invention discloses a hydraulic transformer provided with a combined port plate and belongs to the technical field of hydraulic parts. The hydraulic transformer is characterized in that an outer plate provided with an inner tooth is arranged outside an inner plate provided with an outer tooth in a sleeving mode; the right end face of the inner plate and the right end face of the outer plate are attached to the left end face of a floating plate; the outer plate inner tooth, the inner plate outer tooth and a floating plate convex tooth are located in the same circular ring groove and divide the circular ring groove into a first arc-shaped groove, a second arc-shaped groove and a third arc-shaped groove; a first oil channel of a rear shell communicates with the first arc-shaped groove through a first oil hole; a second oil channel of the rear shell communicates with the second arc-shaped groove through a second oil hole; a third oil channel of the rear shell communicates with the third arc-shaped groove through a third oil hole; the outer plate is driven by a first swing motor to rotate through a spline; the inner plate is driven by a second motor to rotate through a spline; the floating plate is connected with the rear shell through a pin shaft; the swing angle of the inner plate and the swing angle of the outer plate are both within the range of 0 degree to 140+/-10 degrees. The hydraulic transformer has the advantages that the hydraulic transformer has large transformer ratio and is capable of effectively reducing vibration and noise, and servo control can be achieved easily.