The influence of the non-Markovian, dipole-dipole interaction of two atoms and the off-resonant on fidelity of two identity atoms’ quantum state was investigated by means of full quantum theory. The results show that the fidelity of two identity atoms’ quantum state is relatively higher when the two atoms are initially in the entangled state under the non-Markovian regime, especially in the off-resonant case, in which the fidelity considerably increases with interaction of the two atoms. If the two atoms are initially in the separable state, the fidelity of the quantum state is not optimal no matter the Markovian effect exists or not.