Abstract: The present disclosure provides a method for identifying modal parameters of engineering structures based on fast stochastic subspace identification, and relates to the field of structural modal parameters identification. The method includes the following steps: collecting responses; obtaining a unitary matrix by performing random projection on and QR decomposition of a matrix; obtaining a small matrix by projecting a Toeplitz matrix onto the unitary matrix; obtaining U, S, V matrices respectively by performing singular value decomposition of the small matrix; performing eigenvalue decomposition; and determining an order interval. According to the present disclosure, the small matrix is obtained through performing random projection on and QR decomposition of the traditional Toeplitz matrix, the dimensionality of the matrix by singular value decomposition is reduced and the computational efficiency of the matrix is improved.