In the research into helium  mass  spectrometer leakage detection, a method for linearizability investigation has been put forward recently. Meanwhile,  it  has  been demonstrated the rationality of the method through multiple tests based on the study in the principle of constant pumping speed of the mechanical pump in vacuum. The method realizes the control over the pressure through adjusting the leak detector inlet, so as to adjust gas flow rate in the leak detector. The concentration of helium  in  mixed  gas  is controlled via changing helium flow  rate  during  leakage detection, so as to influence value display of the leak detector. With regard to test of linearity of the leak detector, a research has been conducted into relationship between the inlet  pressure  and  output readings. The methodology of the research is characterized by simplicity, convenience, cost effective, and its test range covers  most  of  the  test leakageage rates in practice.