The invention relates to an evaluating system and method based on radio astronomical instrument device electromagnetic radiation. The evaluating system comprises a microwave switch, a receiving antenna, a reference noise source, a signal source and an emitting antenna, wherein two normally-open contacts are arranged at one end of the microwave switch, the other end of the microwave switch is connected to a spectrometer through a pre-amplifier, the spectrometer is connected with a computer, the receiving antenna is connected to one normally-open contact of the microwave switch, the standard noise source is connected to the other normally-open contact of the microwave switch, the signal source is connected to the computer through the network, and the emitting antenna is connected to the output end of the signal source through a radio frequency cable. According to the system and method, by means of the technical index and observation requirements of a radio astronomical observation system, radio astronomical instrument device radiated emission is tested and evaluated, the influence of radio astronomical instrument device radiated emission on a radio telescope is analyzed, so that reference is provided for compatibility design, shielding design and site radio management of the radio astronomical observation system, and the engineering significance is high.