The ion temperature and toroidal rotation velocity with high time resolution (τ∼1 ms) using charge exchange spectroscopy in JT-60U tokamak plasma have been measured. The method uses three interference filters that have slightly different peak wavelengths. These filters are selected according to the ion temperature and rotation velocity expected at the measured position. The system with a time resolution of 1 ms was applied to the analysis of fast plasma phenomena. As an example, the time evolution of the C VI ion temperature and toroidal rotation velocity across the L–H transition has been measured. The toroidal rotation at a normalized minor radius (r/a=0.3) increases gradually after the L–H transition, while that at the edge changes from a speed of 5 km/s before the transition to -40 km/s after the transition within a time of 5–10 ms. © 1999 American Institute of Physics.