With respect to the extended use of polymer nanocomposites, many studies are being conducted in this field. Many researchs were performed on Poly vinyl cloride blends and nanocomposites. Physical, mechanical and thermal properties of these nanocomposites are dependent on the compatibility and the structure of each available part which improving these properties is of great importance. In this research, the effect of adding closite 30B nanoclay on mechanical, physical and thermal properties of poly vinyl cloride is investigated. In addition, the effect of PMMA-g-MAH compatibilizer on the compatibility and dispersion of clay nanoparticles inside the matrix and also on the mechanical and thermal properties of PVC/nanoclay is studied. Nanoclay in four loadings of 0, 3, 5 and 7 wt%, PMMA in four loadings of 0, 5, 10 and 15 wt%, maleic anhydride (MAH) as compatibilizer in four loadings of 0, 0.3, 0.5 and 0.7 wt% and dicumil peroxide (DCP) as initiator in four loadings of 0, 0.03, 0.05, 0.07 wt% for 100 unit weights of poly vinyl chloride were added. Design of experiment was performed using taguchi method and according to this method 16 different compounds were produced using melt mixing by a counter rotating twin screw extruder. Impact and tensile test specimens were produced using compression molding. All the specimens were evaluated using the same experimental conditions. The presence of PMMA-g-MAH compatibilizer inside samples consisting of PMMA and Maleic anhydride (MAH) and dicumil peroxide (DCP) as a consequense of successful grafting was confirmed using FTIR spectroscopy. By studying the results of tensile and impacts tests (sample 8 having 10% PMMA, 3% nanoclay, 0.07% maleic anhydride, 0.03% dicumil peroxide) the best sample was chosen which it's tensile strength, elongation at break and impact strength compared with pure poly vinyl chloride (sample 1) was improved 90%, 62%, 2.6% and 8% respectively. By the addition of nanoclay loading from 3 to 5% and then 7%, as a result of poor dispersion of particles inside the system, mechanical properties were weakend. XRD patterns showed that samples having PMMA-g-MAH compatibilizer and 3% nanoclay, had an exfoliated structure while samples with higher nanoclay loadings had intercalated structure. Thermal analysis of differential scanning calorimetry for samples showed that the degradation temperature compared to poly vinyl chloride was improved. Glass transition temperature of the samples had no significant changes compared with poly vinyl chloride. Keywords: PVC/Nanoclay Nanocomposite, PMMA-g-MAH, Dicumil peroxide,Closite 30B, Thermal And Mechanical Properties Of Nanocomposite.