The invention relates to a construction method of a top plate type main transformer foundation. The method is characterized by comprising the following steps: 1, pretreating a steel plate, wherein the step 1 comprises the following sub-steps: 1.1, selecting the steel plate, and drilling a thread through hole in the steel plate; 1.2, galvanizing; 1.3, preparing anchoring ribs; 1.4 selecting H-steel, and forming waist-shaped holes in the lower wing of the H-steel; 1.5, adjusting the surface flatness of the steel plate; 1.6, arranging the H-steel on the top surface of the steel plate; 2, erecting a die plate, wherein the step 2 comprises the following sub-steps: 2.1 tamping the foundation; 2.2, constructing a net rack; 2.3, constructing an enclosing plate; 2.4, constructing a framework; 2.5, sequentially rotating each spiral pipes to enable the same height of the upper end of each supporting plate; 3, pouring a concrete foundation, wherein the step 3 comprises the following sub-steps: 3.1, pouring concrete by layers; 3.2, hoisting the steel plate, then arranging the anchoring ribs, and placing the steel plate into the concrete; 3.3 adjusting the levelness of the steel plate; 3.4, dismounting fixing bolts, and hoisting away the H-steel from the steel plate; 3.5, levelling and compacting the concrete surrounding the steel plate; 3.6, adding concrete to the thread through holes, and levelling and compacting.