  Within the second-order non-Markovian master equation description, we develop
an efficient method for calculating the noise spectrum of transport current
through interacting mesoscopic systems. By introducing proper current-related
density operators, we propose a practical and very efficient time-local
approach to compute the noise spectrum, including the asymmetric spectrum,
which contains the full information of energy emission and absorption. We
obtain an analytical formula of the current noise spectrum to characterize the
nonequilibrium transport including electron-electron Coulomb interaction and
the memory effect. We demonstrate the proposed method in transport through
interacting-quantum-dots system, and find good agreement with the exact results
under broad range of parameters.
