Abstract: Nanocrystalline Pd modified p-Si electrode (Pd/p-Si) was prepared by electroless deposition on p-Si. The structure and morphology were determined by XRD and SEM respectively. The results showed that the structure of Pd coatings was nanocrystalline and Pd particles with different sizes were obtained by controlling time.The average diameter of Pd particles was about 80 nm at deposition time of 20 min. The catalytic properties of the Pd/p-Si electrode for hydrogen evolution under illumination and in darkness were studied with the constant current polarization method. The results showed that the hydrogen evolution reaction (HER) potential of the Pd/p-Si electrode under illumination was 250 mV lower than that in darkness, and was 450 mV lower than that of p-Si electrode in darkness at current density of 2.5 mA•cm^-2. The results of electrochemistry A.C. impedance spectra (EIS) indicated that the electrochemistry HER resistance of the Pd/p-Si electrode decreased from 593.12 Ω•cm² to 442.20 Ω•cm² under illumination，and its HER rate increased evidently.