Abstarct: The Chah-Musa sub-volcanic pluton is located at the northern part of the Central Iran (Semnan province) and is part of the Toroud -Chah Shirin magmatic arc. The volcanic-pyroclastic rocks of the Eocene are the oldest rocks in the region. In this region, one mafic dike with the EW trend, the thickness of 5-10 meters and more volcanic pluton after the Eocene. This dike in the field has a green color, and microgabbro in composition. Under the microscope, there are also intergranular, intersertal, subophitic and ophitic textures and are essentially composed of plagioclase, pyroxene and olivin minerals, with minor amounts of magnetite and apatite. In the dike studied, the size of the crystals in the center of the two parts (3,2) is larger than the margin. In this study, for the first time magnetic fabric patterns on this dike is divided into 3 separate section in the form of 76 stations investigated by anisotropy of magnetic susceptibility (AMS) method.The resulted data indicate that mean magnetic susceptibility in μSI are as follows: part 1 (16221), part 2 (19908), part 3 (11601). baxsed on these values, mafic dike is ferromagnetic granitoids (500˂km in μSI). Overall, values Km from western to eastern part decreasee with increasing hydrothermal alteration.also, at each station has a direct relation to the amount and size of magnetite grains. The percentage of anisotropy (P %) values vary from 0/9 to 6 and indicate that the percentage of anisotropy in stations with lower alteration rates is also low in anisotropy. The study of magnetic foliation and lineation patterns in part 3 indicate that fabric pattern of this dike is similar to the strike of dyke. In parts 1, 2 magnetic lineations dominantly oriented to the southeast and the dip in the center of the dike are almost vertical. Magnetic foliations mainly show in part 1 (049,14), part 2 (245,26) and part 3 (18,10) trend. On the other hand, due to the high slope Lineation and negative T parameter in section 3 seems that it is possible feeder zone. In general, On the basis of the position of the average magnetic lineation and the polarity of the foliation plate, parts of 2 of mafic dike expressed the magnetic fabric confirms Interstital fabric and part 1, 3 expressed Normal fabric. According to tectonic studies and asymmetric pattern obtained, microgabbroic mafic dike emplacement with a transtension regim.