The invention discloses a 4H-SiC Schottky barrier source / drain MOSFET device with field plate terminal protection and a manufacturing method thereof. The manufacturing method includes the steps of performing a standard cleaning process, depositing field area silicon dioxide through a field oxide LPCVD method, performing photoetching on an active area, performing HF bleaching, depositing polycrystalline silicon through a standard LPCVD polycrystalline silicon deposition process, doping the polycrystalline silicon, injecting phosphorus ions, etching the polycrystalline silicon, etching plasmas, sacrificing an oxidized sample 1, performing ion injection annealing, performing 1050 DEG C N2 atmosphere annealing, corroding and sacrificing an oxidation layer sample 1, performing HF bleaching, performing the standard cleaning process to form gate oxide and a side wall, performing annealing to 1050 DEG after oxidization, performing N2 atmosphere annealing, performing photoetching on a source / drain contact area, performing HF bleaching, performing photoetching on a metal lead to form 150nm metal electrode evaporation Ti, performing peeling, performing alloy annealing, and performing 700 DEG C N2 atmosphere annealing, wherein the device comprises a substrate and an epitaxial layer. According to the 4H-SiC Schottky barrier source / drain MOSFET device with field plate terminal protection and the manufacturing method of the 4H-SiC Schottky barrier source / drain MOSFET device with field plate terminal protection, the problem that transconductance and conductance resistance output characteristics of the device become poor due to the fact that 4H-SiC MOSFET is too low in inversion layer mobility ratio is better solved.