Abstract: Negative hydrogen (H-) ion beam extraction measurement experiment was conducted in the Penning ion source developed by Institute of Fluid Physics. The single electrode, double electrode and tri-electrode extraction methods were applied for the preliminary experiment. The experimental beam intensities are much higher than the theoretical calculation result of space charge limited flow. Thus, we present a new method called beam measurement of electrical shielding box. This paper describes the basic principle of dc beam measurement of electrical shielding box method, the CST numerical simulation of the beam trajectory and the experimental results of beam measurement extraction. Employing the V3/2 law of space charge limited flow to fit curve, the beam current will reach 4 mA when the extraction voltage is loaded to 40 kV.