Abstract: On the basis of chaos theory and the assumption that deterministic map equation can be used to describe discrete dynamics of trajectory evolution in reconstructed phase space, a model is developed for predicting pressure fluctuation in fluidized bed. Comparison between the chaotic invariants (Correlation dimension, Kolmogorov entropy, the spectrum of Lyapunov exponents) of measured and model generated time series of pressure fluctuation shows that they are nearly the same. So, the model has captured some important nonlinear dynamic characteristics of the real system. The long-term unpredictability of pressure fluctuation and its exponent separation were also studied .