We synthesized Pd nanoparticles on the surface modified single walled carbon nanotubes(SWNTs) with 3rd generation NH2-terminated poly(amidoamine) dendrimers. We found that the more amine groups are attached on SWNTs, the more Pd nanoparticles are bound. The palladium nanoparticles are attached about 12.1wt% on the hyperbranched poly(amidoamine) modified SWNTs and their mean diameter were 3.3 ± 0.6 nm and 2.4 ± 0.9 nm. A thermal treatment of the Pd nanoparticles functionalized SWNTs resulted the increase of sensitivity, in consequence of getting close between SWNTs and Pd nanoparticles modified on dendrimers. The sensor exhibited to fast response time, and good selectivity hydrogen gas at concentrations as low as 10 ppm.