Charged‐particle detection is one of the most sensitive methods to find the evidence of possible cold nuclear fusion. Using the pulsed electrolysis method, we have increased its sensitivity further and tried to detect weaker reactions of cold nuclear fusion. Charged particles were detected by a silicon surface‐barrier detector. The detector was set under the bottom of an electrolysis cell and closely to a thin palladium‐foil cathode. The electrolysis current of the D2O cell was intermitted at regular intervals of about several hours. The foreground (with electrolysis) and background (without electrolysis) were measured alternately. The data at the same phase of the electrolysis current were put together, so that the effect of the background radiation were reduced and the signal‐to‐noise ratio was improved. The experimental results of counting rates and the energy spectrum indicate that some kinds of nuclear reaction occurred in the cathode.