The pulse length and off-resonance errors in an atom interferometry caused by the laser parameters drift, the atomic velocity, and the electromagnetic field environment will degrade the performance of the atom interferometry. To improve the accuracy of an atom interferometry, these errors should be eliminated or compensated. In this paper, we proposal an approach to optimize the splitting and mirror Gaussian pulses to improve the tolerance for the interferometry environment. The numerical results show that not only the fidelity of the atomic state obtained under the interaction of a Gaussian pulse with atoms is higher than that gotten under the rectangular pulse atomic interaction, but also the fidelity under the interaction of the optimized Gaussian pulse is the highest and the bandwidth of the fidelity is the largest. Furthermore, the Gaussian pulse sequence consisting of optimized Gaussian pulses can effectively improve the interference fringe contrast of the atom interferometry. [ABSTRACT FROM AUTHOR]