The decoherence of two initially entangled qubits in anisotropic band-gap photonic crystal has been studied analytically without Born or Markovian approximation. It is shown that the decoherence dynamics of two qubits in a photonic crystal is greatly different from that of two qubits in vacuum or that subjected to the usual non-Markovian reservoir. The results also show that the finite-time decoherence invoked by spontaneous emission could be suppressed efficiently and the entanglement of the Bell state possessing odd parity is more easily preserved in a photonic crystal than that of the Bell state possessing even parity under the same condition. A store scheme for the entangled particle pair is proposed.