The properties of plasma often depend on the following factors: (1) the composition of plasma, such as atoms, molecules, ions, electrons, chemical groups, etc. (2) The state of particles, such as neutral state, excited state, ionized state, activated molecules and free radicals. (3) The number density of all kinds of particles, i.e. the number of particles per unit volume. (4) Temperature of various particles. If the temperature of electrons and ions is equal, it is called equilibrium plasma; conversely, it is non-equilibrium plasma. The environment of plasma, such as electric field strength, magnetic field strength, electrode structure, gas flow, discharge vessel, etc. The action time of various factors.