The purpose of this research is to investigate the diagenesis processes of Amiran Formation using petrographic evidence. For this purpose, the Morani and Pirshamseddin stratigraphic sections in southern Lorestan were selected. The lithology of Amiran Formation in the studied areas , The lower boundary of the Amiran Formation in the sections studied Gurpi Formation, and its upper boundary is erosional discontinuous with the Kashkan Formation. Developed diagenetic processes as well as replacement processes have been observed in this formation. In some cases, fossils or fossils with a healthy shell and without any fractures or wear in them are filled with debris in the sandstone facies, so that only traces or ghosts of fossils remain. can be seen In some cases, the replacement by detrital material is selective, so that there is a relationship between the size of the replaced seeds and the size of the shell of the oysters. In the shell of Alokums or fossils that have a larger size, the seeds are easily placed in the shell of these fossils. But in the case of allocames or fossils that have a smaller size, the detrital grains could not enter the space of the fossils, so they are less affected by the replacement process. . Based on petrographic evidence, the paragenetic sequence of Amiran Formation deposits in these sections has been interpreted in four environments: marine, freshwater, burial and uplift. Three stages of diagenesis initial diagenesis , middle diagenesis and final diagenesis have been determined for the studied deposits.