The MIR-0AS is a user-fnendly software to be used for macromolecular structure determination by multiple isomorphous replacement method with optmized anomalous scatteing on X-ray crystallography. The software is designed to be flexible，allowing users to solve macromolecule structure without a good knowledge of X-ray crystallography. The graphical user interface is written by Tcl/Tk，and the programs to calculate for MIR-0AS are written mainly by standard Fortran 77. The MIR-OAS runs on wide range of architectures and operating systems.