The invention provides a low-temperature microscope cold source system, which uses a high-pressure nitrogen refrigerant as a cold source; a semiconductor refrigerating plate is used to pre-cool nitrogen gas, and the nitrogen gas is throttled; and a PID controlled electric heating mode is adopted to make the nitrogen gas regulated to a needed temperature in a tempering room, and the nitrogen gas enters an objective table. The system is characterized in that: a nitrogen tank is connected in series with a pressure stabilizing and reducing valve, a high-efficiency heat exchanger, a high-efficiency heat regenerator, a second throttle valve, the tempering room, and a low-temperature objective table through a copper pipe in sequence, and an upside-down type low-temperature microscope is arranged below the low-temperature objective table; the high-efficiency heat exchanger is connected in parallel with the semiconductor refrigerating plate, and the second throttle valve is connected in parallel with a second electromagnetic valve; the inner part of the tempering room is connected with an electric heater, and the outer part of the tempering room is connected with a PID regulator; and the inside of the low-temperature objective table is provided with a micro thermocouple. The system has the advantages of simple structure, safety and reliability, no moving parts, high systematic stability, accurate temperature control, low consumption of the nitrogen gas and the like.