The master equation for the microcavity-quantum dot coupled system is established based on the quantum regression theorem,and the time-dependent evolution of the density matrix of the two-level system for a quantum dot in a microcavity is studied under pumping by laser pulses.The characteristics such as the number of emitted photons and the second-order corelation function are derived from the density matrixes.Parameters of the microcavity and the pumping conditions are optimized for single-photon sources.T...