Abstract: The Pd nanoparticle in diameter of 6～76 nm has been prepared by microwave high pressure synthesis procedure, using sodium citrate as reducer to reduce Pd(Ⅱ) to small Pd nanoparticle(crystal seed),polyacrylamide(PAM) as stabilizer and reducer for the crystal seed growing. The TEM show that there are sphere Pd nanoparticles. There are a absorption peak at 216 nm for citrate and a absorption peak at 205 nm for PAM. There is no absorption peak for Pa nanoparticle in the spectral range of 200～800 nm. The absorption value increases with the wavelength decreasing. There are five resonance scattering peaks at 470 nm,510 nm, 400 nm,800 nm and 940 nm for the Pa nanoparticle in diameter of 6～76 nm at a lower concentration.