To clarify the influence of mixing on chemical reactions, the effects of convective and diffusive mixing on the spatiotemporal structure of the concentration field in a Lotka-Volterra. periodic reaction is analyzed. At the beginning of mixing, concentration distribution is not uniform spatially, and the oscillation mode differs at every position. After a long time, however, the concentration becomes uniform throughout a whole system, and then synchronizes and oscillates with a unique period. The whole concentration field is regarded as an assembly of concentration oscillators. This assembly is a dynamical network of short-range interactions due to diffusion and recombination caused by convective flow. With this model, the process to final coherent oscillation mode and the factors affecting on it were analyzed.