A general expression of quantum discord for X structure density matrix was derived. The dissipative dynamics of non-coupled two qubits independently interacting with their reservoir was solved by the non-Markovian master equation in a single excitation state. Under the detuning spectral density, the quantum discord dynamics was discussed and compared in different coupling regime. The results showed that this expression was employed to any physical system having X structure density matrix, and the two variants of master equations were exploited in different coupled regimes in the description of quantum correlation dynamics. It is convenient to calculate the quantum discord for later study and provide certain reference about what kind of master equation used in different coupling areas.