Abstract: Single-ended mixers were designed and made with ADS software. A set of mixers of different damage levels were then obtained after effects experiments of microwave injection. By measuring diode volt-ampere characteristics and analyzing failure mechanism, the paper establishes the damaged diode model through fitting. Based on this model, the equivalent circuit of damaged mixer is established. The simulation values of conversion loss are in accordance with the experiment ones. The model places a shunt resistance parallel connected with the junction resistance of normal diode, and the resistance is quite correlated with the damage level of the mixer. The smaller the resistance is, the more serious the damage is.