Abstract: By using the adjustable spin filtering model, the effect of the magnetic field and the electron transition energy interval change on the spin electron filtering properties are calculated and discussed firstly. The study found that the changing of the magnetic field and the electron transition energy interval cause the electron tunneling probability and tunneling conductance to show the quantum step effect. As the magnetic field increasing, the electron cyclotron frequency and the Zeeman energy levels splitting have been strengthened at the same time. This then leads to the transverse binding force is strengthened in the quantum point contact, while the spin filtering effect is weakened. When the magnetic field is given, the electron transition energy interval is smaller, the spin filtering effect is much more obvious. Consequently, as the electron transition energy is changed, the shape of the saddle-like potential and spin filtering sensitivity are changed too. For different materials, consider the role of both the magnetic field and the electron transition energy interval to find the best spin filtering result. More importantly, the quantum point contact structure can be easy acquired through the standard electron beam technique, so these study results give the theoretical support for designing new spin filtering devices with bright application prospects and the potentially commercial value. Morover, if the spin filter substrate is fabricated by use of the high Landau factor materials，the spin filter performance can be further improved.

Key words: quantum optics, quantum point contact, spin filter, saddle-like potential, quantum conductance