The invention belongs to the technical field of engineering structure monitoring data analysis, mainly relates to a method of identifying false mode of an engineering structure and particularly provides a structure false mode identifying method based on different data selection characteristic system realization algorithms. Truncation order nt is judged preliminarily, data selection is changed according to the truncation order nt, a data movement stability diagram is drawn, and a structure false mode is identified accurately from the data movement stability diagram. The influence of an environment upon frequency is observed by changing data selection, the influence of the environment upon a true mode may be reflected directly, and the false mode may be identified accurately.