The method of freedom condensation was adopted to condense the computa tional model when the modal data were insufficient to identify the structural da mages, and a formula was given to calculate the residual force vector of a reduc ed model. It was proved that the residual force vector was sensitive to the dama ged element. An improved residual force vector method was presented to decrease the error influence caused by condensation and measurement. Firstly, the damaged structure was measured to obtain the residual force vector matrix. Then the mat rix was compared with the one of undamaged structure to get the difference matri x. The biggest absolute value in each row of the difference matrix formed the im proved residual force vector. The improved residual force vector was defined to locate the suspected damaged elements preliminarily. Then the damage degree was estimated by the screening method. The numerical simulation shows that only seve ral of the previous natural frequencies and modes are needed to detect the damag e quickly and accurately, and the method has a better antinoise capacity.