In order to improve the sensitivity of optical coherence elastography,we propos e a multi-order phase differential method,which can be used to reconstruct elastic images of bi ological tissue by measuring micro-displacement.In this method,a piezoelectric transducer wi th the driven frequency of resonant frequency is used as the external mechanical excitation s ource.The micro-displacement can be extracted by obtaining the changes of phase between t he adjacent time points and performing multi-differential operation on the extracted phase.The first experiment is made on a phantom including an inclusion.The inclusion in the phantom can b e identified from the surroundings clearly.The result verifies the feasibility of our method and its high sensitivity.The second experiment is made on a lung tissue with tumor of a mou se in vitro.2D and 3D optical coherence elastography images are obtained to achieve the elastic imaging of the tumor.It i s easy to find the tumor location in the organization.The experimental results of tumor tissue show that this method has high practical value in the diagnosis of micro tumor edge,and it can clearly identify the micro tumor tissue and surrounding normal tissue through the elastic images.