The aim of this study was enhanced the absorption of electromagnetic waves by nanocomposite containing polyaniline (PANI), functionalized multi wall carbon nanotubes (MWCNTs) in the presence of magnetic Ba 0.2 Sr 0.2 La 0.6 MnO 3 nanoparticles (NPs). At First MWCNTs was functionalized by 3:1 ratio of sulfuric and nitric acid, then functionalized MWCNTs was coated by NPs with the traditional sol-gel method. In the final step, MWCNTs/NPs covered by PANI with an in situ polymerization in an aqueous solution. FESEM, XRD, vibrating sample magnetometer (VSM), FTIR analysis was confirmed NPs synthesis in appropriate size and shape and functionalized MWCNTs was coated with NPs and PANI synthesized by correct chemical formula covered all of them, too. The maximum reflection loss of the Ba 0.2 Sr 0.2 La 0.6 MnO 3 NPs and MWCNT/Ba 0.2 Sr 0.2 La 0.6 MnO 3 were about-12.04dB at 14.82 GHz and-22.36 dB at 14.78GHz with a bandwidth of 2.67GHz (more than-10dB). The conclusion indicated we could good microwave shielding in KU-band (12-18 GHz) by these nanocomposites.