Abstarct: Chah - Musa sub-volcanic pluton is part of the Turoud – Chah Shirin magmatic belt and located in the northern part of Central Iranian Structural Zone. Volcano –pyroclastic sequences of Eocene including of volcanic breccia, agglomerate and red tuff are the oldest rocks within the studied area Porphyritic andesite of Chah - Musa pluton is cut volcanic –pyroclastic sequences.. In microscopic examination, main minerals are plagioclase and hornblende and fewer amounts of biotite, magnetite and apatite. The texture of the rocks is mainly porphyry, glomerophorphyry, sieve and zonation of plagioclase. Since the andesitic rocks of the region kind of porphyry plagioclase species. Therefor they are suitable examples for crystal size distribution (CSD) studies. The crystal size distribution (CSD) is the relationship between the crystal size and the density of the crystal. Three dimensional forms of plagioclase crystals and their residence time are calculated by integration of microscopic image processing and crystal size distribution method. According to calculations in the baxse of CSD slope diagram, the natural logarithm of the density of the crystalline density (n) is drawn up against the length of the crystal (L) Plagioclase phenocrysts available in the andesite rocks of region, in time limited 118/62 -630/7 years have been grow in magmatic chamber and have nucleation of 1.4×10-8 till 9.27×10-9 mms-1. Crystal size distribution diagram product of coarsening, fractionation and Accumulation and magma mixing or population mixing of crystal in region illustrate. Evidence of petrographic like porphyry, glomeroporphyric, microlitic porphyry and unequilibrium texture like zoning, sieve texture in plagioclase Confirmation of the contents of CSD diagram.