The invention provides a false identifying method for a modal parameter of an ocean structure. The false identifying method comprises the following steps: A) acquiring an actual measured signal of the ocean structure; B) separating, smoothing and reconstructing the actual measured signal of the ocean structure; C) constructing an identifying core matrix for the modal parameter of the ocean structure; and D) identifying if the modal parameter of the ocean structure is false. According to the false identifying method, the defect that a false mode must be considered for identifying when the false mode is stronger than a target identifying mode is overcome, the modal identification of an ocean engineering structure is realized by utilizing the smallest core matrix and the engineering application prospect is wide.