The invention discloses a space environment simulator heat sink temperature self-control system and method. The system mainly comprises a controller, two PID parameter adjusters, two PID controllers, a refrigerant valve controller, an electric heater controller, a communication unit, a temperature collector, a temperature sensor and a space simulator heat sink. The method comprises the steps that the temperature difference signal between the heat sink temperature and the target temperature is fed back to the PID parameter adjusters and the PID controllers; and a refrigerant output power valve and an electric heater are used as actuators to affect the heat sink until the heat sink temperature reaches the target temperature. According to the invention, PID self-control is introduced; the shortcomings of large thermal inertia and slow response speed of the heat sink temperature are overcome; full load operation of a refrigeration system is avoided; the device loss is reduced; the service life of equipment is prolonged; unnecessary refrigerant waste is reduced; the test operation cost is reduced; and the system and method have an important engineering application value.