Abstract: The system and the method of the Ag－ and He collision experiment are described, and the distinguishing feature of this experiment system is that only one detector was used. The single-elect rondetachment cross-sections of Ag－ in collision with He has been measured in the energy range of 5~30keV by the growth-rate method. The typical value of the cross section of Ag－ impacting on He at 20keV is 6.6×10－16cm2. The experimental uncertainty of the results is about ±8% in this work.