The invention discloses a method and system for determining the elasticity modulus of a composite material. The method comprises the following steps: determining an elasticity modulus calculation formula of any point in a to-be-measured area of the composite material structure in a weak form according to an oscillatory differential equation in a one-dimensional structure form of the composite material, and recording the elasticity modulus calculation formula as a weak form elasticity modulus calculation model; and according to the weak form elasticity modulus calculation model, determining a calculation formula of the elasticity modulus of any point in the to-be-measured area in a weak form under the broadband excitation condition of the composite material structure, namely the broadband excitation elasticity modulus calculation model. By adopting the method and system for determining the elasticity modulus of the composite material provided by the invention, nondestructive, in-situ and local elasticity modulus measurement can be carried out on the composite material. Moreover, a weak calculation mode is adopted, so that the problem that the signal-to-noise ratio is reduced due to the fact that the high-order partial derivative of the vibration displacement is solved can be avoided.