A strain measurement method based on the microstrip patch antenna sensor is introduced, in which the resonant frequency shift can be utilized to measure strain. An antenna sensor with a rectangular antenna patch radiates at two fundamental modes and the resonant frequencies of the two fundamental modes are determined by corresponding electrical length of the current flow. An applied strain changes the dimensions of the microstrip patch antenna, resulting in the electrical length change has different influences on the electricity flow as well. Therefore, the applied strain information can be collected by the changes of antenna resonant frequencies. Four kinds of microstrip patch antenna sensors with different dimensions were designed and manufactured to measure the strain, the results show that there is a strong linear relationship between the resonant frequency shift and the strain. Besides, the sensors have more sensitivity at higher initial resonant frequency, which is in good agreement with the theoretical analysis. The research can provide a preliminary theoretical basis for the application of this technology in the wireless structural health monitoring.