Abstract: This Paper analyses the particularity of the corrosive condition of steel frames of the plant greenhouse. In view of the high temperature, high moisture, chemical fertilizer, pesticide and high oxygen produced by plant photosynthesis and acid water membrane formed on the surface of the steel frames which can conduct electric current, the theory of using additional electric current cathode protection was advanced. In the greenhouse the controlled experiments were made on the basis of parameter of chosen protective volt of-850 mV and protective current of 80 mA/m². The result shows that the corrosive capacity of the steel frames almost equal to naught after using additional electric current protection. However, without protection the corrosive capacity of the steel frames is as 27 times great as that of those protected.