Abstract: The breaking performance of vacuum switches is closely related to vacuum arc plasma characteristics, and analyzing arc particle distribution is significant for improving vacuum circuit breaker breaking capacity. Based on continuous spectral radiation theory and the light intensity ratio diagnosis principle, this paper proposes a microscopic observation method for arc plasma, and investigates the effects of different contact breaking modes (direct pull, rotation), materials (pure copper, CuCr alloy) and structures (flat plate, cross-shaped) on the distribution of electron temperature and electron density in vacuum arc plasma. The results show that compared with direct pull breaking, at a typical rotation angle of 2.4°, the electron temperature decreases from 2.5×10⁴ K to 1.5×10⁴ K by about 40%, and the electron density decreases from 9×10²⁰ m⁻³ to 4.5×10²⁰ m⁻³ by about 50%. A three-dimensional vacuum arc plasma model is established to simulate the rotation effect on electronic parameters of vacuum arc, verifying the diffusion effect of contact rotation on vacuum arcs. Chromium in CuCr alloy contacts inhibits ionization, with electron temperature and density reduced by approximately 23% and 22% compared with pure copper contacts. Cross-shaped contacts introduce a transverse magnetic field to accelerate the arc vacuum transition from aggregation to diffusion state, with electron temperature and density reduced by about 30% and 43% compared with flat plate contacts.