In order to solve the problems of damage identification of rocket skin by modal test in engineering， that is difficult to obtain the higher order modes， and the degree of freedom of the actual structure measurement points do not match the degree of freedom of the model. A damage identification method based on Guyan polycondensation and uniformly distributed load surface curvature is proposed. The translational and rotational degrees of freedom are condensed to the normal upward by two Guyan polycondensation of the cylindrical shell skin model. Then the modal shape of the normal direction is taken as the input parameter， and the damage identification index is constructed based on the curvature of uniform load surface. The damage identification effect of this index on the rocket shell skin has been analyzed numerically. The results show that the polycondensation model can fully meet the engineering requirements， and the method can be used to identify not only the single damage location but also the multi-damage location， which can also give the relative damage degree. This have great practice application value to the damage identification of rocket skin in engineering.