We propose in this paper a data compression scheme for large-scale particle simulations, which has favorable prospects for scientific visualization of particle systems. Our scheme deals with a time sequence of particle data obtained from simulations as a set of individual particle trajectories and compresses it by approximating each trajectory as a piecewise polynomial function that satisfies a given tolerance; for each approximated trajectory, a piecewise polynomial is determined so that the deviations from the original trajectory are smaller than the tolerance at all data points. The approximated trajectories are continuous within the entire time interval and therefore the particle position can be evaluated everywhere in the interval. The scheme is also capable of using an independent time-step for each particle. We name this concept TOKI (Time-Order, Kinetic, and Irreversible) compression. In this paper, we show an application result in the plasma particle simulation data by the data-compression scheme under this concept.