A method of identifying damping coefficient matrix in exponential non-viscous damping systems on the basis of modal test is proposed in this paper. By solving a constrained optimization problem, the optimal modified damping coefficient matrix satisfying the system characteristic equation is obtained; and considering the non-completeness of the modal parameters obtained in the actual mode test, the damping coefficient matrix of the system can be accurately identified by using the limited low-order modes. Whereas with the gradual enhancement of the non-viscous characteristics of the system, the number of modes needed to accurately identify the damping coefficient matrix will gradually increase. Furthermore, a method of updating the imaginary part of the complex mode，which can be greatly affected by noise in the modal test，is proposed to satisfy the characteristic equation of the exponentially damping system in this paper; and as a result, the damping coefficient matrix can be accurately identified by using the updated complex-modal imaginary part. And since the less research on the recognition of the relaxation parameter, the identification methods of relaxation parameter which is independent of the imaginary part of complex mode is proposed in this paper based on the modal updating method. And then, through numerical studies, the applicability and effectiveness of the damping identification method and the complex modal correction method for the exponentially non-viscous damping model are verified, and the accuracy of relaxation factor recognition method is proved. Finally, the modal parameters of a cantilever beam are identified through the vibration test, and the applicability and rationality of the exponential damping model are discussed.