A multiple reference impact testing method using long-gauge fiber optical sensors and the related data processing approach are proposed.First,macro strains of key structural elements during the impact testing are measured through long-gauge fiber optic sensors,which subsequently are used to estimate the strain frequency response functions(FRFs)of the structure.Second,a modified CMIF method is proposed to estimate strain modal parameters from the strain FRFs,and corresponding displacement mode shapes are calculated by applying an improved conjugate beam method.Finally,the strain flexibility matrix of the structure is identified by using the identified strain and displacement mode shapes.Examples investigated successfully verified the effectiveness of the proposed method for structural strain flexibility identification.