Elastic modulus is an important indicator of safety of masonry structure. Through the dynamic measurement of 500 groups of ambient excitation and 35 groups artificial excitation on six brick masonry specimens,the paper obtained the basic frequency of brick masonry specimens.It identified the feasibility of basic frequency of brick masonry specimens distinguished by ambient excitation. According to the relationship between elastic modulus and basic frequency, the elastic modulus of masonry specimens can be calculated under ambient excitation. The results agree well with the values of experiment and the current specifications.The results can provide basis data for the further study of damage identification of masonry structure and finite element analysis.