Abstarct: Chah Zard granitoid pluton with 5 km2 extent and 535.4±3.2 Ma age (baxsed on U-Pb zircon method carried on the Zircon grains) intruded into late Neoproterozoic mextamorphic baxsement rocks (Jandagh complex) and emplaced in it. Essential minerals of this granitoid are orthoclase, biotite, quartz and plagioclase. baxsed on geochemical properties and abundance of the biotite and orthoclase, Chah Zard granitoid pluton is S-type granite and has been produced from partial melting of continental crust. In this study, for the first time, emplacement mechanism of the mentioned pluton, and or later affected parameters on it, investigated by anisotropy of magnetic susceptibility (AMS) method. Because of high mylonitization of this granitoid pluton, its magmatic microstructures have been disturbed and tectonic microstructures have been more dominance. baxsed on the field and petrographic observation, this granitoid pluton suffered medium to high grade mylonitization. 114 cylindrical cores and 608 samples from 23 stations have been taken. Magnetic parameters of these samples have been measured in the magnetic lab of Shahrood University of Technology by MFK1-FA machine. Evolution of magnetic parameters of the obtained samples, indicate that mean magnetic susceptibility (Km) in µSI are as follows: mylonitic biotite granites (111.59), mylonitic leucogranites (59.6) and mylonitic surmicaceous enclaves (461.48). Biotite is the most important magnetic carrier in these rocks. This study indicate mean magnetic susceptibility of biotite granite (main part of Chah Zard granitoid pluton) is significantly 100-150 SIµ lesser than common mean magnetic susceptibilities of granitic rocks. Microscopic investigations show that alteration of biotite to muscovite due to reacting with hydrothermal fluid during mylonitization, is important factor in decreasing of magnetic susceptibility of biotite granites. baxsed on the interpretation of concentration and abundance of magnetic lineation and foliation, we can suggest that the major part of magnetic lineations have very low plunge and array or oriented toward northwest. Also magnetic foliations have low dip near to horizontal. Considering the field observation and baxse on the magnetic parameters data, indicate that primitive magmatic structure have been obscured and we can’t use them for determination of feeder zone or intrusion (injection) place or how intrusion of Chah Zard granitoid.