Abstract: In order to realize precise and quick data processing for the neutron residual stress diffractometer at China Advanced Research Reactor (CARR), the Levenberg-Marquardt (LM) algorithm was applied to analysis of neutron diffraction peak position for stress measurement. The object function for peak fitting, the flow chart of the diffraction peak position calculation based on the LM algorithm and the corresponding Labview program were described in detail. Then, a series of diffraction profiles were fitted by the program, which shows that the program could precisely and quickly tell peak position. So the program could be applied to the precise and batch data analysis of neutron residual stress diffractometer.