The invention discloses a large-area molybdenum disulfide field effect transistor based on a high-k gate medium and preparation thereof. The field effect transistor comprises a Si substrate, a HfO2 gate dielectric layer of which the film surface roughness is 0.21-0.65nm, a single layer molybdenum disulfide triangular plate conductive channel of which the field effect thickness is 0.7-1.0nm and metal source and drain electrodes which are arranged on the conductive channel, wherein the Si substrate, the HfO2 gate dielectric layer and the single layer molybdenum disulfide triangular plate conductive channel are laminated in turn. The thickness-controllable HfO2 gate dielectric layer is grown and prepared on the Si substrate through ALD. The single layer large-area MoS2 triangular plate conductive channel is directly grown and prepared on the gate dielectric through CVD. The field effect transistor has great back-gate voltage regulation and control characteristic, the field effect mobility is greatly enhanced, the size of MoS2 is large, the repeatability is great, the yield is high and time consumption is low so that preparation and industrial production of the MoS2 large-scale integrated circuit can be realized.