A dynamic load identification method based on structural strain response is proposed. The research first conducts a theoretical analysis of structural dynamic response and derive the strain expression of structural dynamic response. And the dynamic excitation identification method is then constructed based on the strain response of structure. To improve the accuracy and efficiency of dynamic load identification， the number and orientation of strain gauges is optimized based on the D-optimal algorithm. Finally， taking the dynamic load identification of square cantilever thin plates and automotive trailing arms as examples， the identification of sinusoidal and random loads is carried out respectively. The error sources of the excitation identification are analyzed. Results show that the square thin plate excitation is in good agreement with the original excitation， and the waveform of the trailing arm excitation is basically consistent with the original signal.