A new micro electric propulsion，micro-cathode arc thruster (μCAT)，is introduced. The μCAT is based on the vacuum arc process where an arc flows through a medium between two electrodes. The high ionized plasma is produced by the cathode spot ablation and then spell out to produce the thrust. The magnetic field is applied to focus the plasma plume and increase the specific impulse. A lot of researches on the μCAT have been conducted in the foreign institutes，and the μCAT has been verified on orbit in USA. In China，Beijing Institute of Control Engineering (BICE) has made breakthroughs in the key technologies including uniform ablation on the cathode，low voltage discharge，magnetic field design，etc. The influences of magnetic fields on the thruster are studied by experimental measurement. And the numerical simulations are conducted to obtain the plasma information in the thruster and plume region and study the work process and mechanism. The research will lay the foundation for engineering applications.