Abstract: The diffusion of the vacuum arc in laser triggered vacuum switch (LTVS) determines multiple key performances of the switch, such as trigger delay time, discharge power and high-frequency interruption capacity. In this paper, dynamic diffusion processes of pulsed vacuum arc in LTVS are investigated based on detachable vacuum chamber and arc images. The effects of materials of Ti+KCl mixture on LTVS trigger delay time and interruption capacity are analyzed. Combined with arc magneto hydro dynamic (MHD) simulation, the physical processes of the development and distribution of pulsed vacuum arc plasma during the arcing period are analyzed. The results prove that the irradiation of the laser beam on target materials heats the materials, triggering them to evaporate and ionize to produce a large amount of initial plasma and resulting in the fast triggering of LTVS. Due to arc thermal erosion, the target materials remain a strong plasma source, affecting the process of arc diffusion and gap discharge. The released particles from the target under the thermal effects of the vacuum arc during the interruption period will affect the current interruption capacity of LTVS. It is suggested that the target materials of LTVS should be reasonably designed according to the actual application requirements to improve the related performance parameters.