The invention provides a large-power high-frequency-stability microwave energy generator. The large-power high-frequency-stability microwave energy generator comprises a circuit part and a microwave device part. The circuit part comprises a control protection circuit, an anode power supply, a filament power supply and a magnetic field power supply. The control protection circuit is controlled by a programmable logic controller (PLC). The microwave device part comprises a magnetron, an electromagnet, an upper pole shoe, a lower pole shoe and an excitation chamber, wherein the anode power supply is a high-frequency high-stability high-voltage switching mode power supply. The magnetic field power supply is a high-frequency high-stability low-voltage stabilized current switching mode power supply. The filament power supply is a high-frequency high-stability low-voltage switching mode power supply, wherein high-voltage isolation is performed on the input and the output of the filament power supply. The large-power high-frequency-stability microwave energy generator has advantages of improving stability and reliability of the magnetron and prolonging service life of the magnetron.